There are a lot I like, I wouldn't even know where to begin since the issues are up into the 130s now!
Favorite character: I'd say Brian is one of them. Mainly because they developed him into a deeper character than the rest. There was one storyline where things with him were getting a little creepy. I sort of wish they elaborated on that little bit, but they got some complaints about the storyline getting too dark.
Some of the funniest ones are the non-Hackmaster related ones. Like they're playing a board game or doing something a little different.
I usually like any strip where it focuses on the Black Hands gaming group. They're really cut-throat with each other and their GM is more authoritative.
Patty's Perps is another gaming group that they focus on sometimes as well. They're probably a little less dysfunctional than the other two groups.