Team Fortress 2 has an amazing little console command that every game should implement immediately. By simply typing "explode" in to the console your character instantly does just that: explodes.
Everyone I know and their dog's have the command bound to a key for quick gibby access.
Personally I use it during the post-game time to spray the walls with my beautiful blood. Others sometimes use it to confuse enemies. Some people (kpros) use the command if they are about to die by fire, since using it (or it's relative 'kill') stops the pyro that set you on fire from getting the point(s).
Some people used to type 'kill' during Counter-Strike games for hilarity purposes, however we often found 'nade suiciding to be far more entertaining. Or jumping off the top of the castle.
The Co-Opp guys and I were recently stacking a fairly old HL mod, "Dystopia", and during gameplay I was heartbroken to find that explode was non-existent. This is a command that every game from now on simply needs to have.
Even COD4 would be far more entertaining with randomly exploding soldiers. Oh wait that already happens with the 'nade spam on -FF servers.