Wooded areas with thick undergrowth are an absolute must. A kick-ass trench system in the middle of a field would be a huge plus in my books (and a great way to test out the tornado grenades), although probably not realistic.
I agree with Saint about Saigon, but I wish it was more 'cluttered' (how many times has a group been trapped behind the school buses with nowhere to go?)
Perhaps creating a few fixed objects would be useful for more organized scenarios like: defending a pumping station, bombing an artillery placement, or recovering sensitive military documents within an enemy camp.
Personally, I wouldn't mind spending more to play on a field that has some of these items.
Call sign: Shadow_Matter
"I play airsoft, yes yes..."