I've actually just recently decided to give up caffeine. I think it will save me a lot of calories too. Usually at school we'll go to Startbucks so now I won't spend money on overpriced coffee and I'll be saving like 200-500 calories per visit!! Also, I'm going to start biking to work every morning and there's a Tim Horton's right next door. I can't bike and drink a coffee though so again I'll have to miss out.
Finally, we also have this amazing coffee machine at work (I work for Italians so they like their coffee!!) It's a Miele coffee machine and it makes really good coffee, I think that's going to be my biggest challenge, but I will refrain.
Sorry for the lengthy reply, but I'm starting with caffeine with the intention of being able to give up other things as well. I figured caffeine was a good start. Next.. CHOCOLATE