Yeah, I don't really have a particular favorite. I do like Wyeast London ESB, because of it's ridiculously clean flavors and super-high flocculating properties. Unfortunately, the only batch I made with it (outside of a cherry stout that masked its properties) got infected somehow. SO disappointing. I had this awesome london ale while it was in secondary. I dry-hopped it and aged it...you wouldn't believe how clear and delicious it was at bottling. Then...the first bottle...cloudy...sour...gusher...BASTARD!
Oh well. Gonna use it again someday.
I'm also a fan of pacman, and Wyeast Abbey Ale (very spicy!). So far, the Wyeast Bohemian Lager has produced a fabulous, clean pils, but it's not done lagering yet, so the verdict isn't completely in.