On sale with steam. Easily the best $5 game I ever played.
Defender's Quest is tower defense meets RPG. You recruit party members as you level; earn/purchase armor and weapons. Customize party members by choosing which skills to invest in. Make your team composition however you like (I love Rangers). Captures that "one more fight before I stop... no really... uh ok and another" essence.
http://www.defendersquest.com/
