R100GSPD Gutless, lots of shaking, noisy screen, heavy. And that was a well-sorted one with WP suspension and lots of love. Made my Tiger 900 feel like a GP bike. Yet much more recently, riding an R80GS on gravel, and then another sorted R100GS with Ohlins boingy bits, both seemed much more tolerable. Not spritely like I enjoy most, but well-rounded, satisfactory nonetheless and entirely fit-for-purpose.
H-D something or other, fairly basic 80ci softtail IIRC. Rented one for the day while on holiday in Hawaii, for a relaxing pootle around. Ergos completely all wrong for my body shape and size. Two-fifths of fcuk-all cornering clearance. Quirky handling that varied with speed differently to anything else I've ever ridden. I wanted to like them for what they are, but every positive thing seemed to be drowned out by several related negatives.
KDX125. I've ridden lots of little bikes and enjoyed them, but this thing had nothing below band, and only a fairly narrow band at all. I thought it'd be a peakier but weaker version of my 200EXC, or like a DR200 but with more zing, but it was just devoid of power. Maybe a longer ride would have helped, but in the end I was spanking it and wanting more all the time even when it was on the boil. Perhaps it wasn't jetted right, or something. Climbing off the 640A straight on to the 125 on rough, hilly tracks wouldn't have helped.