I was once at a wedding where the best man made the speeh into a funny story. He gave loads of interesting facts from when the couple met, to their first date to the proposal. The best man got 2 of the grooms friends to give him a hand writing it and they contributed some funny stories which where suitable to the audience of elderly relatives in attendance.
Do you mean his bachelor party or at the wedding? It doesn't matter what you do really just make sure the right people attend and take care of everything, he should have to get a round of drinks or ring a taxi or worry about anything. Take charge of the night and make sure he gets to fully relax. He and his wife to be have been doing a lot of planning, thinking and worrying, it is all about giving him a break.