My d20 modern group has developed a couple.
1. Beatrice: Beatrice is an old lady who has almost killed the pc's on two occasions. They were rolling 2's and 3's to hit, and she was getting numbers in the high teens and even crit'ed a couple times.
2. Crown Vic: The PC's have some fascination with car jacking and one of the first questions they ask whenever they come upon a road or parking lot is "Are there any cars to steal?" I use the "fickle finger of death" method to determine cars, inevitably there's always a Ford Crown Victoria.
3. Hospitalized: If a player is unavailable their character is randomly hospitalized.
4. Ninja Nurses: One of the PC's who was hospitalized felt the need to "escape" from the hospital. She decided to attack the nurses. The nurses have the same luck w/ dice rolls as Beatrice. She parachuted out a window to escape.
5. 97th floor: This developed from the hospital escape above. The conversation went like this.
PC: I smash open the window with my IV stand.
Me: okay, the glass will probly shred the iv bag...So there are a bunch of junkies trying to lick up the morphine...
PC: Okay, I jump out the window.
Me: (looking up falling damge rules, never thought I'd end up using 'em and all....

)
PC: Wait what floor am I on?
Me: Umm...(evil grin) the 97th.
6. Battle Tupperwear: This is realworld slang for the mostly-plastic Glock pistol. If I need an NPC to have a generic gun, its a glock, so the player's see alot of these.
7. Morphine: For some odd reason, the pc's decided that morphine is the main ingredient of medical kits...
