Brave Frontier - If you like RPGs. It's F2P, but they aren't hyper-aggressive with promoting in-app purchases. Probably my favorite mobile game
Sonic Jump Fever - Probably the best Sonic game made in years, and all you do is jump
Giant Boulder Of Death - Endless F2P runner, but you control a boulder destroying the Riccola cough drop village
Major Mayhem - F2P; They love wiping out saved games w/ updates so don't get too attached
Smash Hit - F2P; You throw pinballs to break glass; good arcade feel, not dikkhard about in-app buying either