Sunburst Finishes, especially cherry sunburst & shitburst (I think the correct term is tobacco sunburst)
Oil finishes
Open Pore finishes
Relic'd finishes
Pearl scratchplates
Basses that don't have a passive tone control
Looper pedals, especially when used by acoustic guitarists at open mic evenings
Keyboard players - never worked with one that wasn't a complete & utter c**t