I don't think I have a favorite beer since I rarely drink anything twice. There are a bunch of craft beer places in Philly and I like to go and pick up 6 different beers. I recently had an Ithaca Flower Power and that was one of the best that I've had. It was an IPA, and pale ales are pretty muh my favorite style, and the flavor was fantastic.
Victory Brewing Company also has some pretty great stuff out there. Helios would be my favorite of theirs but it's really hard to find. I've only come across it in 24oz single bottles. It's probably the craft beer that I've had more times than anything else.