This app was mentioned in 3 comments, with an average of 23.67 upvotes
Besides obvious picks like Crashlands and Downwell:
Biobeasts, because it's kind of like One Finger Death Punch meets Nuclear Throne.
https://play.google.com/store/apps/details?id=com.BattleOn.BioBeasts
Chess Runner, because it turns Chess into an arcade game and actually manages to be fun.
https://play.google.com/store/apps/details?id=com.Daliblue.ChessRunner
Rocket Ski Racing, because it feels like i'm playing Extreme G or Wipeout.
https://play.google.com/store/apps/details?id=com.nocanwin.rocketski
Call Of Commander, because it's the sequel to Call Of Snake which we never got.
https://play.google.com/store/apps/details?id=com.magiccubegames.callofcommander
Sky Chasers, because it's a Nintendo like twist on Lunar Lander platformers.
https://play.google.com/store/apps/details?id=com.luckykat.skychasers
Corerona, because although it came out mid-December it's still an awesome bullet hell puzzler that's completely free.
https://play.google.com/store/apps/details?id=de.booxware.gaming.gameone