My favorite comic is Hark! A Vagrant, it's a very history geek sort of comic. XKCD is usually good as well, being a different sort of geeky
I've recently started reading Basic Instructions, which I'm enjoying quite a lot. My wife just got the Lackadaisy book which is
gorgeous and quite funny, but the online strip updates infrequently.
Girls with Slingshots is pretty good and at this point it's the only strips I follow that update daily. I should probably try and get back in to Wapsi Square, I enjoyed it quite a lot before it became far more fanciful and my wife told me it's reigned that in a bit recently.
There are a few strips I check every few weeks, often because they have a slow update schedule or because their content tends to be rather hit-or-miss: Three Panel Soul, Goblins, SMBC, Punch an' Pie, Subnormality, and probably a few others I'm not remembering off the top of my head.
When it comes to gamer comics the only one I still follow is Penny Arcade. I gave up on RealLife not long after it started and stopped following PvP several years ago; Control Alt Delete never did much for me.
I recently stopped following Evil Inc. Although I was never really in to super hero comics I enjoyed Evil Inc for quite some time but the last few months haven't done anything for me. I dropped The Book Of Biff around the same time. They're still worth checking out and they both have large archives for someone with a lot of time to kill