A day in the life of_________
Depending on the venue, outside is preferred for clean up, you auction of items for what the groom to be might do/have in a day. For example, "Bob" starts his day with a shower - you auction off a pail/bucket of ice water and the winning bidder gets to dump the ice water on the groom. Next would be breakfast and you would have coffee grounds, maybe pancake mix, maple syrup, orange juice, eggs - all as separate auction items. Be creative with their favourite foods for all the meals. Whatever activities they like to do, make that apart of it. Ie. Likes to fish, needs bait, auction off a can of sardines to be dumped on them. The people doing the dumping will be creative as to how and where they dump, rub and pour the items on the groom.
Tons of laughs and lots of money will be generated from this. Just keep a garden hose ready for the clean up or lots of tarps if doing it indoors and close to the shower. One stag we did this at raised over $1000 on this auction alone.