I don't really have a favorite but I love living in the Lansing area because it seems everyweekend there is some fair or festival going on. Alot of stuff even during the winter.
Usually start it off with the Blessing of the Bikes (BOB) in HELL, MI. (May 22nd this year). Then it's the Bay City Fireworks for Independance Day, River Roar and 4 x 4 runs to wherever to finish it off.