GoNNEr. I thought it was just a classic platformer with cool graphics, today I finally played it and I was hooked as the gameplay reminds me of an evolved Downwell, an obsession of mine. Really addictive, and yesterday I was complaining that I couldn't find anything I really wanted to play in my library.
I actually have Downwell in my library (it was cheap, only $3, and that's regular price), but have yet to try it. I got it because it looked like a nice game if I want something short (permadeath mechanics aren't as much of a problem when the game is meant to be played to completion in one sitting). I have seen speedruns of that game, but of course, since it's procedurally generated, it feels like it would be better to aim for a good consistent time than to go for a personal best. (Then again, speedrunning isn't my thing, though I do enjoy watching it.)
Of course, I have been playing Tangledeep, which is a true roguelike and fairly long (particularly if you do all the sidequests and upgrade your equipment) lately, and have been really enjoying it. (There's a mode where death only sends you back to town with loss of half XP, GP, and JP, so I don't have to risk having to start all over; then again, on my current run I have reached 15F and haven't died yet.)
(Bonus points: Tangledeep's protagonist is female, as are the majority of named characters (not counting random champion enemies), it seems.)
Edit: Decided to check the GoNNER trailor, and the music is an immediate turn-off.