I've got one vintage F/S knife back in the day for pretty cheap to go in the very small collection.
I'd be partial to one of these trench knives:
http://www.rockislandauction.com/vie.../1024/lid/3994
But that's a pretty big price, and they're not legal to import here.
I guess it's all how you look at it.
Randall knives of WWII or Vietnam vintage can go for some really crazy money that make these look cheap.