I guess I just don't understand. What is it that makes a Russian fur hat, canadian fur hat, cowboy hat, smokie bear/ranger hat OK with a kilt, yet a tweed flat cap not? In my eyes, ALL those options are much more discordant. The only folks you'll see wearing a smokie bear type hat (if it's what I'm thinking of...)

http://www.cowboyhatstore.com/campaign/campaign2.htm

are park rangers, state troopers and drill sargeants. and this....

http://www.tundragear.com/602/black-tundra-hat

Girl not withstanding, a Ushanka would look perfectly silly with a kilt. My tweed flat caps are at least irish in origin/manufactur and to my eyes look alot more appropriate than many of the other suggestions given. I'm really missing why they are viewed as such a fshion "don't" by some.