Splosion Man
Splosion Man, with its dead-simple controls and pleasant aesthetic, is a breeze to get into. I imagine that casual players will quickly be turned off, though, by the sometimes devilish puzzle/platform difficulty. For me, it's a treat.
What I'm not so big a fan of is the game's occasional Mega Man-style challenge: platform segments where you don't even know you might die, until you do. And which require split-second precision to get past, else you're sent back to a checkpoint that always seems just a little too far back.
Splosion Man is surprisingly fun for its simplicity - a testament to its level design - but also more frustrating than I think it has to be.
Progress: Level 1-11