I'm surprised no one mentioned the best features of the FN, which is that the bolt carriers are interchangeable without needing to be fitted by an armourer and, in the C1A1 at least that the charging handle doubles as a beer opener!
Also, I'll never forget the joy some herbies experienced coming out of the head at Chiliwack and finding their trigger group dis-assembled on their rack!
Lastly, if you adjust the gas plug just right, when you fall in and order arms the gas piston assembly flies off across the parade square... . ah, the good old days.