What is your most surprisingly good cleaning tool

[MEMERC7]

Just cleaned our car last night and wiped all the water off immediately after cleaning with the Autoglym One Pass tool. I was sceptical about buying it as it cost over £20 but it follows the contours of the cars so well and gets all the water off better than a chamois cloth! I can highly recommend this to everyone. So what car detailing tool did you buy with scepticism and now would you not want to do without?

Used one on a solid black car - never again because despite a thorough washing the blade left micro-scratches. Cost of blade irrelevant it will always mark the bodywork. BUT I used one when washing my company cars (when not put through car washes) which I always ordered in silver as they seemed to look cleaner for longer & of course not bothered about scratches.