Fave House Robot?
They were all ace but my faves have to be Shunt and Killalot.
Shunt was able to do some serious damage with his axe, I don't think any of the contestants came up with an axe to rival his. He was pretty durable too, perhaps only vulnerable to flippers. I remember one episode where he totally dismantled Hypnodisc.
Sir Killalot - well, he was just a bad ass, a great addition to the show. Pretty much indestructible and once he decided the fight was over, it was over. Perhaps his only weakness was his poor manouverability, and the fact that Sgt Bash repeatedly set him on fire lol.
Matilda and Death Metal were cool but their saws only ever did surface damage to the contestants, and they didn't seem to be built as sturdily as Shunt. Matilda pretty much got trashed in every battle! Bash was pretty useless unless one of the contestants was flammable and he nearly always ended up getting flipped.
I can't think of any others off the top of my head...there was the ref-bot I guess, he didn't really do much, but he was useful when he could give the robots a nudge that got stuck on the side-wall for example.