This one has to make the list because it was the first webcomic I really got into. To be honest, I haven't followed it in years. The cast got pretty large and a lot of various subplots developed that I just lost interest in. This is an example of what I call "narrative" style webcomics. There is an overarching story that is relatively grounded in reality. These types (which make about half my list) are successful if they create likable characters with interesting stories. That doesn't mean things don't get random or unrealistic, but for the most part things stay focused on the characters. Something Positive has a very cynical and sarcastic tone which just started to wear on me after a while. I do like to check in once in a while and I also really like Randy's side project Super Stupor, but it rarely updates. Here is the first Something Positive comic, which really sums up the attitude of the series. (The art has improved a lot, though).
This is another "narrative" type comic, but it has enough Batman and Transformers jokes to keep me tuning in. The central cast is a group of weirdos that work in a toy store. You can really tell that the writer is an avid toy collector, namely transformers. Frankly, I don't get all the transformers in-jokes but the writer has the seemingly accurate assumption that batman can be funny in almost any situation. Also, Ronald Reagan is a regular character (he's apparently not dead, just working in a toy store) and there's a guy named Ninja Rick.
8. Diesel Sweeties by R. Stevens
Another one that I don't follow regularly but I like to check up on this one from time to time. It features a number of reoccurring characters, but there isn't too much actual story. It's mostly about robots, sex, clever pick-up lines, puns, and hipsters' ironic lack of irony. You don't have to follow this one to enjoy it, but you will probably miss out on a couple of the jokes. The art is simple but enjoyable.
7. Least I Could Do by Ryan Sohmer and Lar Desouza
LICD is all about a rich, good looking womanizer who's addicted to red bull and crazy stuff. Sound like someone you know? No? Not even a little? Well at least I'm addicted to red bull...
I noticed this comic when they did a run where Rayne (the main character) was in a concrete induced dream sequence where he was batman. It was really funny and got me interested. The main appeal for me is the art by Lar Desouza. I really like how he draws the characters. I tried to read the comics before Lar took over and didn't really like them. LICD is pretty wacky, and split into chapters, which is nice. I am getting a bit bored with it, though. A year ago it would have been higher on the list, and a year from now it will probably be lower. He's started doing a blatant Calvin & Hobbes rip-off every Sunday which I find a little annoying...
6. Saturday Morning Breakfast Cereal by Zach Weiner (Tee hee!)
This is the first comic on my list that doesn't have any kind of story. Each comic is a separate entity of funny. I really like this guy's sense of humor, whether it be a witty observation or a dumb pun. He does a lot of nerdy humor, which I find more funny than most people probably will. This comic is good for a quick chuckle or occasional groan (the usual response to bad puns). It also has a hidden punch line to every comic which is a fun little bonus.
5. Amazing Super Powers by Wes and Tony
This comic is very similar to SMBC. Each comic is a separate joke, though there are some reoccurring characters. The art in this one is better in my opinion and while the humor in SMBC leans towards nerdy, the humor in this one is considerably darker. In fact, some punch lines border on wrong, but I still always chuckle. It also has a secret punch line.
4. Questionable Content by J. Jacques
This is my favorite of the "narrative" style comics, though I'm not entirely sure why. It follows half a dozen hipsters through their quirky conversations and love triangles. Also there are sentient computers and ipods. The art has improved greatly since the beginning but I the stories advance slowly and I don't think I get half the indy music jokes. I still follow it though. I just want to know what happens. There's a character, Hannelore, that really reminds me of my wife in a lot of ways, so maybe that's part of it. It really is pretty funny and I do want to see what happens next. (This example reminds me of my wife...)
3. Penny Arcade by Jerry Holkins and Mike Krahulik
If you read web comics at all than you probably have read this one. In fact a lot of people would be surprised that Penny Arcade is not in the number one position. This is arguably the most successful web comic out there. They have published several books and even have their own video game. There are two main characters, Gabe and Tycho, and several supporting characters, but there aint no plot! There is video game humor and violence and plenty of it. The writing is very snappy and the art is great. There is a reason why this is considered one of the best, but it's just not my favorite...
2. Subnormality by Winston Roundtree
This comic is smart, funny, and and awesome to look at. I'll admit that some of the comics are a bit too wordy for me, but if you do read it all, it's almost always worth it. Not all of the punch lines are supposed to be funny, sometimes he writes sad and poignant stories, but they're still really good. I would buy his book if he wrote one. He has a couple reoccurring characters, including a Sphinx, but each comic is stand alone. He also hates Nickleback with a passion.
1. XKCD by Randall Munroe
This is it! My favorite web comic. The art? Stick figures! The humor? Nerdy! But I love it! Maybe it's because it seems like something I could do myself. I am nowhere near that smart or clever though. This is my favorite because it makes me laugh out loud (or LOL) more than any other comic out there. I probably don't get every single joke, because there is a lot of programmer humor, but that's not all there is. If you hold the cursor over the comic, yo get an extra punchline. I love that shit. This comic is just funny, plain and simple. Read it.
Honorable Mention: - The Adventures of Dr. McNinja