Urban fighting's always interested me most. So many places for ambushes, sound reverberates off buildings so you can't place where most shots are coming from.
Eastern Front would be good, I just think I'd make a crap russian, whereas I'd be brilliantly english wandering around in shorts and socks with a brodie helmet on.
How old are people generally in ACW, though? We had a guy from another group join us at our last event, he was nearing 50 but was up until about 4 in the morning one night after sneaking out of the castle we were in and finding a night club (whilst in full soft kit with a templar surcoat over it).
He was still awake before I was too.