I used to love "Bloom County" when I was in high school...and "The Far Side". Although I don't read them much anymore, I do like "Get Fuzzy" and "Non-Sequiter" and "Bizarro".
I used to love Clavin and Hobbes - but I think Dilbert is the most hilarious comic - that and it is down right scary that a lot of what he writes is stuff that actually happens @ my work. Here is one of my all time favorites:
Calvin and Hobbes . . . . one of the greatest along with Garfield.
You guys know that Garfield has been around 25 years and they are coming out with a digitally animated movie!