Got a few. Most notable is my Copen (why is it Kei cars make the best troll mobiles?)
It isn't immensely powerful (80-something BHP) but has enough cornering speed to make up for it. It was built for a friend's Copen one make series with a few friends.
Basic rules were 100bhp, SH tyres, need 2 stops per race, no aero or NOS, only ABS allowed (why would you need anything else?) yadayadaya
How is it a troll car? The looks are the first part. Where others used colours like black and white with some racing wheels in black or gold. Mine? Lotus French blue with some retro style wheels (the ones which look like they were taken from a Beetle) in the same colour. Second? It won half the races in the series and was on the podium for each one despite a 20bhp disadvantage (the tracks I lost at were Monza, due to a lack of speed, Matterhorn, due to a lack of power up the hills and Sarthe, because of a 4 mph disadvantage on all straights)
It looked ridiculous going flat through Eau Rouge (78mph woo!) when the others looked mildly serious, and the car seemed to be able to beat any similar PP car in the twisty bits, RS tyres or not.
They ain't Copin' with my Copen.