When you are just finishing servicing your bike and you're getting a bit excited cos it's near to the time when you can ride it again just stop, have a cup of tea or a beer and chill.
Don't think "I'll grease the rear suspension linkage" and then, after greasing the first one, yank the grease gun and snap the nipple!
Yes I did it, snapped off flush as well so nothing to get hold of to unscrew the rest of it. Luckily I managed to get a hex drive in it to get it out.