Paranautical Activity hearkens back to the days of old school FPS but mixes that with the modern roguelike trend. The gameplay is both fast and frantic and there are tons of items to find to help keep the game varied. If you enjoyed the fast paced shooters of old, then give this a try. It's got some nifty tunes as well.
Doom made Shooters what they are today and THIS GAME STILL HOLDS UP. Nothing like mowing through masses of demons at break neck speed!
While the gameplay can get repetitive, Super Puzzle Platformer Deluxe is a fantastic high score game. With great music and fun mechanics, I can't say I've ever played both a color matching puzzle game and a platform shooter at the same time before. Also this game is difficult....really difficult.
