My boyfriend spent a few years as a bike mechanic, and he doesn't let me work on my bike too much. The last time I tried, I rounded out one of the disc mount holes on my brand new set of suspension forks. Ooops

Oh. And for taking off pedals - for more leverage, try putting a larger pipe (e.g., set of old handlebars, long thin strong pipe) over the handle of the wrench or pedal spanner, and then swinging off that.