Top down rogue-like bullet-hell-ish dungeon crawler - Enter the Gungeon - a million and one things to unlock, the better you get the more you unlock the better your runs. Great retro style.
TowerFall Ascension - awesome 4 player vs mode or 2 player co-op.
Crawl - This game is super fun with 3 or 4 people. You play a dungeon crawler and the other players are the monsters. Kill the player and you take your turn. Can play against AI. Level up monsters and gear as you go. Unique style of game with a very retro look.
Let It Die - i spend waaaayyyy too much time on this rather pointless 3rd person adventure game. But - it is free to play. Note, if you die it costs real money to continue (though you can earn that currency in game, not requiring you to spend much or anything.) I took it super slow compared to some people on how i climbed the tower.
I have dozens of games I have barely cracked into.
