District and "avocation" tartans (firefighter, the tartans associated with various military branches, etc.) can be an excellent choice. It gives the wearer more of a connection to the tartan. For example, Bob really likes his Leatherneck kilt.

There are also tartans associated with non-Celtic family background -- I think the German Heritage has been mentioned -- I have a length of the elusive Dutch Friendship waiting to go under the needle one of these days. . .