Well, I tried not to read any of the previous posts to avoid influence. I'm not going to include anything by Joss. No particular order either.
Ally McBeal: It's like a live-action cartoon set in a law firm! It's such a smart show, very witty and every character is fully developed and fully distinct. Vonda Shepard's music is fantastic, and I love that she receives a credit in the series--her voice really defines a lot of the scenes. "Bygones" cracks me up. I can't really comment too much on the show because I've only watched up to the second season so far, but I haven't watched an episode that I haven't liked.
Futurama: Out of any other show I watch, this one probably best fits into the description of "by geeks, for geeks". Honestly, watch the behind-the-scenes; the producers/writers are very blunt about their geekiness. Smart writers, smart show, silly gags that appeal to the child inside of us go hand in hand with math jokes (math jokes!). Plus, I can relate to Fry. There's one scene between Fry and Leela; she says "Fry, this isn't TV, it's real life. Can't you tell the difference?". His reply: "Sure, I just like TV better."
Gilmore Girls: I love Lorelai, I love Rory, I don't really love Emily but she has grown on me a bit after watching the show over and over again. The story may seem a little corny, based on the premise (mother/daughter best friends blah blah blah) but the dialogue is just fascinating. My favorite thing about the show, though, is that it views people--even the misers (Luke), the over-achievers (Paris, Taylor)--in an positive light. Very uplifting show, but very funny and dramatic in all the right places.
24: My love for this show has worn off the past few seasons, although it's still entertaining. The first 2 seasons, and even the 3rd to an extent, were amazing television. The premise was fresh, the story was tight, the acting was phenomenal, and you know that it had to take a lot of talent to actually script and film a "real-time" show. The latest seasons, like I said, are entertaining, but come across as a little too formulaic. Regardless, Jack Bauer is a fantastic character.
Rescue Me: It's been a while since I've seen this, but I was struggling to find my 5th choice, and just happened to look at my Rescue Me DVDs. Really though, the show is a blast--it's funny, it's dramatic (trust me--the drama cuts very deep, sometimes literally) and sometimes just plain cooky. They go to some territory that other shows will barely even talk about and I often find myself doing the "oh my god!" and doing the half-laugh (you know, when you can't believe what just happened and all you can do is make a quasi-laugh noise? no? just me? okay then). Kudos to Denis Leary, who I previously thought was a one-note comedian. Amazing actor and writer.