Funnily enough with the current craze for name changing, jimi, etc, I had been thinking of changiny name to The Curmudgeon but I wasn't sure could consistently spell the word.
Latecomers who tie their lines over yours.
Latecomers who untie your lines, tie theirs and then re-tie yours with a single granny knot.
Old boaters who have little patience with learners.
1. Idiots who put their shore lines on so that the lines wear away at one's gel coat/transom/rudder/bow all night.
2. Idiots who insist on winding huge amounts of mooring line over a cleat so that no-one else can use it.
3. Boat owners of all description (especially old, curmudgeonly and ugly ones) that moan about mooring fees/marina charges etc. It's called capitalism and without it none of us would have a boat in the first place. (Except a few civil servants and G Brown Esq)