Vice grips, then trash them.
New ones are like $10. give or take.
To install, get a thick washer. Clamp it into a set of vice grips.
Insert washer into the groove, and turn.
PS: If the nipple is locked in and won't budge. Put a torch on the nipple and intake. Get it really hot, and melt wax into the threads. Screws right out.
