I never cook in the microwave, but when I got an email for 3 minute chocolate cake I had to give it a try. I found a similar recipe on Recipezaar so I went with that one.
It turned out pretty good! It wasn't as good as cake from the oven, but it is a great quick fix. Mine was a little on the dry side but I think that has to do with my microwave. I'm going to play around with cooking times. I think that frosting, chocolate syrup, ice cream or something like that would have made it better.
Give it a try! Magic Chocolate Mug Cake
ETA: If you are watching what you eat, be sure to check out the calories first. This is not a healthy dish. It makes a BIG serving so you could easily eat half and save the rest. Or check out the suggestions to replace some/all of the oil with applesauce. You could also use a sugar replacement to cut back some more. I'm going to play around with the recipe now that I've figured it out.