I have 4 taps on my beer cooler so I usually have a variety on tap. Stout or porter on tap 1, Alt, Red or amber ale on tap 2, APA, IPA, or ESB on tap 3 and a Kolsch, Blonde or Wheat on tap 4. Of course there are others that work into the mix as well. The ones that you'll find most often would be.
Porter
Alt
APA
Kolsch