There's a disgustingly effective spot for sentries on Gold Rush stage 2, cap 1 (I believe that's the stage number anyway...) where you can build a dispenser then plonk a sentry down on a truck's bonnet. My usual killing spree with turrets isn't that great, but putting it here garnered 17(!) in a single life.

Either the team I was against had been composed of completely unaware ninnies, or there's something about that location I don't know about.

If you mean the one on Stage 3 cap 1 it's really easy to kill, get beneath it with a demo and lob some stickies up and it's a done deal

Thats a good spot i got 9 there in a comp match It shouldnt have happened but it did, these guys were half competent, so i reckon tis a good spot