Okay, I could be totally wrong here, and I invite correction, but if I'm right, we have our first real indie social game hit.
Stick Run is by Otto Manuel, who has done a series of Flash-portal games, some of which are pretty good, like StickCombat.
Stick Run is a somewhat frustrating sidescroller with, really, only two buttons; jump and crouch. You move automatically left-to-right, and must avoid obstacles in your path. Anything you hit is instadeath. In some cases this is tricky, e.g., jump too soon and you hit an upper obstacle, but not soon enough and you hit a lower one. Graphics are stick-figure primitive, gameplay is fast and brutal, and the music (unusually for social games) does not suck.
It's not a game style that will be unusual to indie fans, and while fun, its hardly innovative; there is, however, a pretty cool multiplayer feature (that is unfortunately hard to get into -- either you create your own game and invite friends or view the chatline and try to get into a game someone spams the name of before the max players fill out).
And when I say "social game hit," I mean it; 1.7m MAU and 300k+ DAU! Not exactly what Zynga aspires to, but for a lone wolf developer out of nowhere with no cross-promo capability, this is huge. The game monetizes with powerups and status bling badges, which is not exactly mainstream, and doubtless leads to ARPDAU far lower than conventional social game publishers look for, but I would guess that at these numbers, Otto is raking in bucks that look extremely good for an indie.
(Via, I am ashamed to admit, Insidesocialgames.com.)