Keeping going...
Rifts:
"It was a dark and stormy night.  Too late Fred the Godling Anti-monster, 
burster realized that it was a ley line storm sent by a evil alien 
supernatural intelligence from another diminsion."

Battletech:
"It was a strom riddin night, the 'Mechs trode cautiously, since there were no 
rules about rain or lightning hitting mechs yet, and no one had windshield 
wipers."

The Livewire
morris.113@postbox.acs.ohio-state.edu

"And Remember Your Highness; The Sun never sets
on the British Empire because God doesn't trust
the British in the Dark" -Sliders

From: martin@shambala.demon.co.uk (Martin Smith) 

Amber:
    King Random decided that it should be a dark and stormy night ...
after all, he had just lost every game in the evening's poker.

GURPS:  
  It was a Dark and Stormy Night, which is Physical, Hard, and defaults to
Foggy Evening at -6, or Bright Afternoon in London at -8.

Paranoia:

"It was a bright, calm nightcycle, perfect in every way thanks to the
wisdom and vigilance of our benevolent friend The Computer. Rumors that
the night was dark and stormy are treason. Please report such rumors
immediately. Thank you for your cooperation, citizen."

rec.games.frp.misc posters:
 
	"It was a <roll> dark and ..."
	"Hey - you don't need a roll to decide a simple matter of ..."
	"Whaddya mean. Quantum fluctuations demand it. Heisenberg ..."
 	"Bull. If it's important for the story *then* make it dark."
	"No way. Roll randomly for cloud cover"
	"Listen, buster, the character I have needs dark to be played properly"
	"Tough."
	"Listen, this is ROLEPLAYING, not wargaming, ya know"
	"Accurate simulation is still needed"
	"But ..."

	...

and of course, (almost verbatim from my last session)

15th level Rolemaster players:

 	"It was a dark and ..."
	"I cast nightvision, sly ears and wolfsense and take first watch"
	"...*VERY* stormy night. Make a resistance roll or catch a chill"

MAGE:
"It might have been a dark and stormy night, but given the paradigm
shifts that had been occuring in the area lately, it's hard to tell. 
Leastways, it isn't raining on Tomas.  The rest of you, of course, are
dripping wet..."

TAPESTRY: (Lisa Steele's game system [Sorry, Lisa])
Lisa (as GM): Ok, so you are going to climb the Pyrenees in the middle of
a very dark and stormy night?  Might I add that it's January 6th and it's
been snowing pretty much daily since November?
Steven (as Sir Etienne):  Ok, so maybe we'll go north to Carcassonne
instead...

STAR TREK:
Captain's Log: Stardate 58917.3   The Life Support secondary systems are
on the blink; it is currently dark all over the ship, even though it's
supposed to be noon, and it is currently raining everywhere _except_ the
holodeck...

WHISPERING VAULT:

As your Circle steps from the bounds of the Flesh into the Corrupted zone, 
you are immediately enveloped by the whispy strands of dark hatred emenating 
>from the Unbidden, as the Enigma falls about you in a torrent of dashed 
hopes, unending nightmares, and broken souls...

Still Going...
  Aliens Adventure Game:
    "It was a dark and stormy night on Acheron. Lighting streaked across the 
     sky and the dim outline of an Alien could be seen clawing a hapless 
     Colonal Marine to shreds"

  Car Wars:
    "It was a dark and stormy night. Dirk had a D2 penatly to his hazard roll,
     which he failed as he was making a turn at 70 MPH in Pase 3. Dirk's car
     vaults into the air, the right tires each take 15 points of damage. The 
     car flies through the air for 4 inches, spinning around it's central axis
     360 degrees then flips over in mid-air, smashing the roof of the car 
     (which has 0 points of armor <- it's all on the sides) into the side of the truck stop,
     the car takes 39 points of damage, which takes out Dirk and his power plant. 
    The AADA earns $20,000,000 from film rights for this crash!

From: Lea Crowe <lea@hestia.demon.co.uk>

Aria:

The Definite Neuter Pronoun was a Nocturnal Period, with a Light (Negative)
Aspect and a high Precipitation Determinant.

In our Werewolf Game...

Al: Tuesday, which coicindentally happens to be the night of the new moon..
<Sudden Eruption blurring out Al>
Jason (Fianna Ragabash): Yeah!! I go get drunk.
Sheryll (Fianna Theurge): Me too! Me too!
Me (Fianna Gaillard): No you don't. We have to wait for any adventure hooks.
Jason: I use Blur of the Milky Eye and Remove my Scent too.
James (Children of Gaia Ahroun): I play with my pet weaver ant Hermen.
Me: What was that Al?
Sheryll: When do we get more experience points? I need a higher Gnosis.
Al: I said it also happens to be raining rather heavily...
Me: Oh, okay I put on my overcoat.
Al: The phone rings.
Jason & Sheryll (pretty much simulataneous): I got it.
Me: How do these people keep getting my number?

Theatrix:

The Role has the Secondary Descriptors of "Stormy" and "Dark", and the
primary Descriptor of "Knight."

Rolemaster:

"It was a <roll, shuffle, shuffle> dark night with a type D weather critical
<roll, shuffle, shuffle> it was Stormy, too.  The lightning startles you and
you <roll, shuffle, shuffle> slice off your left nostril and juggle your 
weapon for 3 rounds as you trip over an imaginary dead turtle, bleed at
3 pts/round and act at -20, no parry."

(Someone else from this site will likely retaliate with a Hero system version
of this shortly...)

Hero system (CHAMPIONS):

"OK, as you head for the Evil Eight's hideout it's a dark and stormy night. 
That means -4 on perception, -3 if you have IR, -2 for UV, Radar, and Sonar. 
Because it's raining HARD, that's why, Tom.  Yes, rain does mess up Radar, I
don't CARE if it doesn't say it in the book!  Running has a Turn Mode,
because it's slippery, unless you have Clinging and don't go noncombat.  Yes,
Dick, if you Teleport you have to make a DEX roll not to slip.  Oh, and
Harriet, your gas-based attack is Reduced by Range as well.  I KNOW you
didn't take a Limitation.  Haven't you ever heard of special effects?  What's
that, Joe?  You're pulling enough Change Environment out of your Variable
Pool to make the rain go away?" 

Hero:

It was a...Phase 1?  Phase 2?  Phase 3?  Okay, make a PER roll, 8-.  6? 
Okay, it's dark.  Phase 4?  Phase 5?  Phase 6?  Okay, make a PER roll,
13-.  10?  Okay, it's stormy, too.  You're hit by a 6D6 Energy Blast, 
Area Effect Hex, Linked to a 3D6 Flash.  You take 21 STUN, 8 BODY.  
Phase 7?  Phase 8?  Phase 9?  Okay, it's _still_ stormy out.  Take 
another 6D6 EB.  Sword Master, your sword is a good conductor.  Take a 
1D6 RKA with that.  Phase 10? ...

AMBER: (take two)

  "It was a dark and stormy night"
  "I'll shift shadows, lose the lightning as we pass the bend in the road, let
the thunder change to the sound of a waterfall and as I pass the old man
standing by the road I'll try for Avalon's skies and hope my brother hasn't
guessed I'll do that. I wonder if this is HIS storm, or should I look to
another sibling for this little gift?"

CHAMPIONS:
  "It was a dark and stormy night"
  "You swine! You know I took a power limitation on my armour 'doesn't
work vs. electrical attacks'!"
  (Players  get into huddle to work out how the man with a gagdet pool can come
up with something that makes them all immune to lightning for a total cost of
2.5 points)

FANTASY HERO:
  "It was a dark and stormy night"
  "You swine! You know I took a power limitation on my armour 'doesn't
work vs. electrical attacks'!"
  (Players  get into huddle to work out how the man with a magic pool can come
up with something that makes them all immune to lightning for a total cost of
2.5 points)
 
SPACE HERO:
  "It was a dark and stormy night"
  "You swine! You know I took a power limitation on my armour 'doesn't
work vs. electrical attacks'!"
  (Players  get into huddle to work out how the man with a tech pool can come
up with something that makes them all immune to lightning for a total cost of
2.5 points)
 
  (That's the wonder of a Generic system: it always works the same, no matter
what genre!)

GURPS: (sorry for the personal venom here)

  "It was a... hang on... Ummmm... where was that sidebar... what's the weather
like? Is that in the rulebook or GURPS: Meteorologists Of Doom?"


WARHAMMER FRP (Enemy Within campaign, anyway):
  "It was a grim and bleak night, the wind howling around the rotting corpses
by the side of the road. The disease-ridden rats crawl around your ankles as
the waters begin to rise form the sewers, flushing out the spiky mutated
twisted horrible and evil chaos denizens of night to perform unspeakable acts 
with innocent young virgins as yet still asleep in their beds."

STAR TREK:

  "Captain, there appears to be some sort of atmospheric electro-magnetic 
discharge from the clouds that is preventing us locking on our transporters...

   Captain, shields have become inoperable!
   (sirens howl)

   Captain, sensors are malfunctioning! The nature and composition of the
darkness energy field are of a type never before encountered!"

   (Console explodes in a shower of sparks and everyone runs from one side of
the bridge to the other).

RUNEQUEST:

  "It was a dark and stormy night"

  The Orlanth Wind Lord starts to pray, the Storm Bull Rune Lord looks around
for some chaos slime to slay, the Nysalor initiate says that the sound of the
storm is merely the smell of one leg hopping and the Lunar hides and hopes that
the red glow round the edges has nothing to do with the Crimson Bat, even a
little bit.

SPACE:1889:

  "I say old chap, looks like we might be in for a spot of inclement weather,
what?"
  "Quite right, old man. Reminds me of the time the mem's hat blew away on
Brighton beach. Shocking! 
  "Corporal Jenkins! Put the pavilion up, double-quick, there's a good fellow!"
  "Yes, sir! Right away, sir! Long live the British Empire, sir!"

  All then proceed with their game of whist while the wind howls around them.
The mem complains about the slight draft as the cards are scattered throughout
the tent for the fourth time. Jenkins is sent outside to hold the tent flap
closed with his teeth.

From: "James H. Jenkins"  <s001jhj@alpha.wright.edu> 

TWILIGHT:2000

GM: "It is a dark, and Stormy night..."
PLAYER CHARACTER, "L-T": "Three watches, make a fire... Is there a wind?
DAMN! COVER THE AMMO!  Crap, OK, Uh... What do you mean my foxhole is
filling up?!?!? Drainage trench?!?! I...OK, (shuffles through old army
traing manual) here it is... Guys...GUYS, Look, (shows picture) dig a
small pit to the left, as deep as your entrenching tool... TRADED IT FOR
A LAW-80?!??!? ARGGH! OK, Look, use a messkit, or something...Traded
that, too??!?!" (turning red, now.)
"OK, at least we can collect the water, use your rain ponchos....WHAT DO
YOU MEAN, YOU DON'T HAVE ANYTHING ON UNDERNEATH??!?  Guess YOU TRADED
THAT TOO, HUH? Crap. Ok... At least the fallout will wash out of the
atmosphere...(To GM): What? Guys, SHUT UP! Huh, A Click? Like a cricket
click, like that? Or like an Ak-47 safety? ....(listens)...TREE
BRANCH?!?!?!  Ahhh!!!! .... Crap. 3D6!??!!?  13. Light. Cool.
....(pause)... "War is hell."


RECON

"It is a dark, and Stormy Night."

"Cool, we'll slip out of the perimeter, in pairs. I'm only taking my
knife, and a pistol...yeah, with the supressor, OF COURSE!"
"Ok, here's the drill. We go out for a snatch & grab, on the VC village
chief at Dak Ben Jiao. Bring some willy-petes, and three claymores.
We'll belly crawl the last 100 meters, as soon as we get a spot on the
objective. Set up a pos on the north end of the village with the '60,
and we do cover and move once we at the hooches.  If you spot a dink in
a spider hole, we're had, grease him, then we'll didi back to the evac
site. PBR picks us up at dawn. Any questions?