There's a scene in the Monsters vs. Aliens movie where the alien antagonist goes "WHAT THE FLAGNARD?" For some reason, I cracked the fuuuck uuup the first time I saw that. I been saying "what the flagnard" for years now.
I also have some 'made-up' insults I'll sometimes drop on people like, "Stop being such an assbutt" or "My mom's being dinosaurbreath again."
Other random words in my daily vocab are:
"Maybebaby maybebaby maybebaby maybebaby--" (I go on and on hoping I can get others to join in on the rhythm lmao)
"DEW IT" (I say it with a very bad Emporer Palpatine impression)
And in a creepy whisper voice I like to go, "Ki ki ki, ma ma ma~" in reference to Jason Voorhees. <3 (Drives my son crazy when I whisper it near him.)
I seriously could go on and on with the dumb shit I say. xD