I was the best man for my dad (yes, I'm female, he wanted his best friend to do it) and he promised I didn't have to make a speech. Then on the day shoved the microfone under my face.... I just thanked them both for the day, congratulated them, welcomed his missus to the family, said how proud we (sisters and I) were of dad and wished them a happy life together. I wouldn't like to have had to think of funny bits or stories to tell though, I'd be embarassed.