My team and I just released a 2D shooter for the iPhone. It's called Sweet Hazard, and it's built around constant movement and tense combat. You fight a neverending zombie horde on a small map, and each of the five weapons is designed to fill a distinct tactical role.
https://itunes.apple.com/app/sweet-hazard/id896494215http://sweethazardgame.com/I might be biased - just a bit - but I think it's a really solid game! I'm still enjoying it, even after playtesting the hell out of it. Learning when the run, when to use which weapons, and how to deal with the different enemy types is something I've found really fun.
Feedback is welcome too! We do plan to update, so fixes and rebalances are definitely possible. And there'll be an Android release before long. Anyway, I'll let some images speak for the game now: