I'm playing the early access alpha of Freaking Meatbags, a real-time tower defense strategy game by Wild Factor.
The game features a series of scenarios with more traditional tower defense missions interspersed with action-oriented adventures. Money earned during missions can be used to unlock new items and better abilities. Your dumb human minions will collect the resources required to build offensive and defensive structures that are usually not restricted in their placement. You can mix the DNA of existing units to produce new units, combining their abilities. Freaking Meatbags is planned for release in late 2014.