Here's a quick recommendation for one of those "hidden" cheap and lesser known games:
Tobe's Vertical Adventure
http://store.steampowered.com/app/105700/
A fun and irresistably cute (seriously, the pixel art is just gosh darn adorable) little treasure hunting platformer with a neat premise and some pretty damn clever level design. You descend down a cave while collecting various treasure in the form of coins and little treasure chests and you'll be rescuing tiny pixel animals as well. Once you reach the bottom of the cave a big chest will be waiting for you. Unlock it and the cave starts to crumble. Now you need to be quick and escape the cave before the timer runs out. With everything falling apart, some blocks and walls have now disappeared, changing the level design ever so slightly and opening up shortcuts and new paths to previously unreachable treasure. So even on the way back up you will have to keep an eye out for collectibles. But thankfully you can plan for this during your descent.
It's a cool idea that works surprisingly well. It strikes a great balance between careful exploration and frantic platforming. It's fun to explore each cave first and find all or most of the collectibles without being pressured by a timer, and then finally having to speed-run the hell out of there once you've reached the very bottom.
Collected treasure and rescued animals unlock health, extra lives and gadget upgrades (the latter are rarely used to begin with). The game has two separate story modes for the two main characters plus a co-op mode. It also has native controller support.
I have only played up to the last world of Tobe's campaign so far. It doesn't seem to be a very long game, that's for sure. I suspect you can play through both stories in about 3 to 4 hours total. No complaints here though, especially at the current price point. I'm not sure if the co-op mode is an entirely separate campaign.
The game's two major flaws are the somewhat stubborn and difficult to master controls and the all too frequent physics and collision glitches. The good news is that you'll eventually at least get used to the former.
Summer Sale Price:
Europe: 1,12€
US: $1.24