This app was mentioned in 6 comments, with an average of 2.17 upvotes
Alley Avenger has 45 levels and has Google achievements and leadership boards. It's a hack'n'slash shoot-em-up style parallaxing runner. Beating the game can be difficult, but getting achievements and purchasing all the power-ups is much harder!
The one I'm talking about isn't anywhere that can be downloaded (not even close), but I made one before this for Android called Alley Avenger.
I'm gonna go with some lesser known ones since people have been mentioning popular games. In the past, I've played Alley Avenger a TON. More recently, I've been playing Horn, which is actually really well made.
Alley Avenger
My latest game for Android. Free, no IAP, and a fun little hack'n'slash shoot-em-up side-scroller to play while you're on the pot.
More importantly, I've recently set up a twitter account where I try to share content relevant to game developers, as well as progress on my next game: West Wars!
And of course, MY BLOG!
This community has done so much for me when I started my first game. I hope with my blog and twitter I'll at least be able to give back a modicum of what I've received.