I've been playing Test Drive Unlimited for a while now and absolutely love the game at it's core it's a fantastic single player experience but the online aspect makes it amazing.
Some if the things that have brought a smile to this old gamers face:
Bumping into random peeps and going for a big blast around the island.
Going for a drive and finding sneaky jumps into locked areas.
Chatting to cool like minded people around the world.
The thing that made me laugh most of all happened last night, I finally made it into the big airport and was having a blast on my bike and there was this annoying kid trying to knock me off, so I sped off and and he chased me, I got way in front of him and stopped just in front of some water, I could see him chasing me down so I waited for him and moved out of the way at the last minute. Next thing I know he is taking a bath cursing me as he goes, that had me grinning for a long time.
So share your stories about online shenanigans that have left you grinning.