You can commute on virtually any bike. Since different commuters' routes, distances, weather and other factors are so varied, what makes an ideal commuter is really individual choices. My commute is fairly long (32 miles round trip), with lots of hills and decent pavement. I ride year-round and we get a lot of precipitation. So, my ideal commuter bike is reasonably light weight with mounts for fenders and racks. I've got several bikes that meet those criteria and I commute on all of them -- which include two touring bikes, a sport touring bike, and a cyclocross bike. If I had to pick one to keep, it would probably be one of my touring bikes or the sport tourer.