I have a couple favorites that come to mind right away but I will most assuredly be back to post more. I'm actually surprised these were reference immediately. Oh well, I'm happy to recommend these one to you guys. They are both and endless supply of hilarity
rofl VG Cats- These tend to be one page comics about current and past video games. The poke fun at everything. Its a giant parody of every game you may have played in the past. There will be times that you will likely say to yourself, "I cant believe they actually fekken went there!", but thats what VGcats does, they go there and they've done a pretty damn good job at it for the past few years.
Penny Arcade- This one does the same kind of thing that VGcats does but i think many would argue that it does it better. I don't know for sure but I think this web comic has a lager following than most other web comics. It is currently featured in a gamer's magazine though I cannot recall which, I believe it is Nintendo Power or Playstation Magazine. This is an exceptional web comic though I don't feel I am giving it's fair due here. I guess the first suggestion for a web comic sapped most the enthusiasm out of me. lol Anyway this is a very hilarious web comic and wonderful art as well.