A Gardiners sill brush.
I've had one in the van for at least six months. Never liked it much, it just felt horrible so it only gets used for conservatory finials and black sills. Anyway today I was gutter cleaning with a flocked Xtreme and I snapped the resi-neck - bugger!
Out comes the red monster and off I go again - blimey this stiff brush is twice as quick on the gutters. So impressed I've ordered a spare.
Don't know why I never used it before.