I use US-05, S-04, or Nottingham if I'm making a beer that accentuates malt and/or hops over yeast flavor. I would also never buy Wyeast 1056 or WL 001 because US-05 is a version of the same yeast (it is also cheaper and contains far more yeast cells). I also found out that Wyeast 1099 and S-04 are the same strain after buying 2 activators for my recent brew (rage).
If I were to make a Belgian, I would consider liquid yeast, however Fermentis actually has 2 styles of Belgian yeast which I'd probably try first (T-58 and T-33) unless I was going for something very specific. If I was brewing a lager I would probably go with a liquid lager yeast, bu I don't really like lagers so this isn't an issue for me.
Apart from that, if I were making a clone of a specific beer, and the actual yeast used by the brewery was available in liquid form but not in dry, I'd go with that. Here's a list:
http://www.mrmalty.com/yeast.htm