Other questions you could ask is where did you get the file from It might be some ranom extension used by some other generic program that's even more obscure to find on google, or specific for some game

My first choice for file types I don't recognise is open the thing in notepad/wordpad or frhed/other hexeditor of your choice to see if you can glean any useful info from there, since a lot of usable file types will be obvious from the first line or few characters or so