Shimano Deore M591 rear derailer - 17138
This is a good old rear derailer that'll never let you down. The Deore was introduced in about 1985, and there have been probably 15 variants, all "Deore" since then. It's Shimano's M.O. All of them have worked well, no surprise, since the Deore is a Shimano derailer after all, and it is in the upper chambers of the derailer line, and is arguably -- and we'd argue it --- the best value.
High Normal (not RapidRise) action. Black cage, with a decent-looking silver body. One of the better looking Deore derailers in the last 15 years.
Shifts to 36t. An excellent choice, always. Nobody, but nobody, ever squawks about a Deore.
Shimano code name RD M591 SGS