The daily sketch. Many artists use them as a warm-up exercise before hitting the comics page. I've flirted with the notion of incorporating it into my routine on and off for years, but like any exercise regimen, it's easy to fall off the horse.
I'm trying it again with my pals at Go! Go! Illustration. My hope is that "working out" with a group will help keep me in the routine.
Right now I'm in the middle of an exploration of characters from the Masters of the Universe cartoon/toy/comics series. Normally I don't like drawing characters created by other people (unless I'm paid for it!), but I'm finding that I'm having a lot of fun with these. I'm doing my best to walk the line between the cartoon iterations and the toy designs, along with a high degree of energy:
Go! Go! Illustration website. I'm also selling the sketches, in case you're interested!