Che Guevara: good or bad??

I keep seeing pictures of him on shirts and posters and I always thought to myself, what was he famous for?? I saw a picture of him somewhere with a quote under it that stated, "Think like him" or something along the lines of that. Were his views good or bad so I'll know if the poster was just a bunch of BS and won't follow it. Was he a good or bad person?? If you don't have a definite answer provide some info on him so I can gather my own opinion.