Well, my favorite online experience was rumbling in monster truck madness 2.
Basically 8 players would have to reach a summit, where they would get points for the time they are up there, while also trying to knock other players off the summit. When you fell, you lost 50 points and your points counted down until you got back up. Throw in some wonky physics and it was really fun and competitive. Heres a basic one that shows off how it essentially works. http://mtm2.com/~tracks/P2012/demotivationalrumblebykmaster.jpg
you knock each other off then have to drive back up.
And a few I made http://mtm2.com/~tracks/P2003/cliffhangerbyslayer.jpg http://mtm2.com/~tracks/P2003/rooftoprumblebyslayer.jpg http://mtm2.com/~tracks/P2004/upmorewallsbyslayer.jpg http://mtm2.com/~tracks/P2003/icerumblebyslayer.jpg
Graphics are pretty ugly in the game but since we all love indies, graphics don't really make a game more fun.
He who stumbles around in darkness with a stick is blind. But he who... sticks out in darkness... is... fluorescent! - Brother Silence