FTL: Advanced Edition
This is one of the most perfectly balanced games I've ever played.  I've come one shot from beating the end boss, but that final kill still evades me.The great part about the game is that the beginning portion is actually quite strategic despite the battles being very easy.  You really need to maximize your wins by either getting in as many battles as possible per sector or by killing opposing crews without destroying their ship.  Your first 5 or so sectors really set the pace for the later game.