What should the file name extensions be?
.fusounds good to me, *.fu is Wind in Japanese (風, as in 風船 pronounced ふうせん, fuusen, engl. balloon), but then there is the urban dictionary FU which is not so nice.
.fused for Forth and Fortran source code.
.fsnice, my initials, but used for F# source code.
.funsuggested by Achim: seems to be unused, sounds good. Is Fuzion functional enough to use this?
.fussuggested by Achim: seems to be unused, close to F.U.S.S.
.fzFits well as a short form of Fuzion, used for a CAD tool called Fritzing, also short for friendzone, and the initials of Frank Zappa, which should be reason enough to choose FZ!
.fumfor Fuzion Module sounds ok, it is an outdated English word for a mythologic chinese bird 凤凰 (Fenghuang).
.fappthe urban dictionary is destroying this again: fapp, but maybe this is less used than FU.
.fpipfor Fuzion Platform Independent Program, but sounds a lot like the Python package manager.
.fpiafor Fuzion Platform Independent Application, might work.
.fsapfor Fuzion stand-alone application
.fuirsounds like you want to run away, but ok.