I was just there and I can't think of a better city to hang out with a bunch of friends. See if any of these appeal to you:
Savannah Slowride – this is one of the funniest things I’ve ever seen—it’s basically a big table with stools and at each stool is a set of pedals to make it ride like a bike. You can actually pedal and drink at the same time (Savannah allows open containers, believe it or not). You can even do a pub crawl on it
Segways – this isn’t as original but it might be fun to do a Segway tour of the city together
Kevin Barrys Pub is a lot of fun—great Irish pub with all kinds of fun Irish bands
I can’t think of anything more fun than to take a “Haunted Tour” with a group of college friends and the ones in Savannah are a blast. It’s a very, very haunted city! “Ghosts and Gravestones” is an excellent one to go with!
There are lots of companies in the area that charter boats—why not go in on one together and see Savannah by water? Here's a suggestion to get started:http://www.savannahboatcharters.com