If you're not already familiar with Mobigame, that's one problem we're going to fix for you right now. They're likely best known for the Edge series of games, and right now you can own their entire catalog for less than the price of a single Subway foot long. Anyway, you can feel safe blindly mashing the "BUY" button on all of these games, especially the free ones:
Edge, $2.99 - Infamous for the drama caused with trademark troll Tim Langdell, Edge spent most of its early life bobbing on and off the App Store as Mobigame and Langdell duked it out. Whenever Edge popped back onto the App Store it'd shoot up the charts from all the people waiting to snag this fantastic isometric puzzle platformer.
EDGE Extended, $2.99 - Half sequel, half expansion pack, Edge Extended takes everything that was great about the original Edge and kicks it up a notch. I'd start with the original Edge first, as the improvements made in Extended make the first installment feel old and busted, comparatively.
Perfect Cell, $1.99 - I feel like Perfect Cell is the secret love child of Chair Entertainment's absolutely fabulous Xbox Live Arcade title Shadow Complex combined with aliens and gesture controls that really shine on iOS devices. The game can be played covertly using stealth, or you can turn the entire compound into a total bloodbath completing the game by force. (Or a mixture of the two.)
Cross Fingers, Free - Tangram puzzles have been done to death on the App Store, but Mobigame manages to make Cross Fingers feel new (and dare I say, exciting?) through clever puzzle design, great graphics, and an incredibly challenging arcade mode.
Truckers Delight, Free - This game is based on the first segment of the entirely ridiculous and potentially not-work-safe video Truckers Delight. Originally there were plans for episodic games based on the rest of the video, but I'm guessing the Apple approval process got in the way of that.