No particular order
Seinfeld - I never bought into how "brilliant" the early years were how they could do a half hour show based on nothing but their brilliant observations on mundane situations. It seems a tad arrogant, though I'm probably confusing praise from critics with what the shows creators actually said. Anyways, I much more prefered when they ditched that format after the first few seasons. My all-time fav episode has to be the one where Kramer finds the Merv Griffin set in the dumpster.
The Simpsons - I could literally spend several hours just listening to people quote entire scenes from the show and enjoy myself. And I have. Of course, alcohol was involved.
South Park - This one tends to be more "hit" or "miss" with me depending on the episode. I think that it would be hard to watch say, half a season and not be offended/disgusted by at least something from that show. That said, once in a while they hit one out of the park. Stan's dad( Randy) is usually good for a laugh.
Flight of the Conchords - I've only seen one season and probably would list this show my #1 favorite all-time. I don't have HBO, but the first season DVD only cost something like 20 dollars. I recommend it, FWIW.
Moonlighting - This was popular a tad before my time, but my parents both enjoyed and taped the show. I became more familiar with it in my teenage years. It was pretty well written.