The greatest of all time was Blendo:
Designed by Jamie Hyneman (of Mythbusters fame). It consists of a 5hp lawnmower engine powering a circular saw blade, encased in a dome made from a wok. The thing was so dangerous Jamie almost lost a foot starting it up (using the ripcord to start the lawnmower engine).
It was undefeated. It tore the ever-loving hell out of anything it faced, frequently launching dismembered parts of its opponents into the crowd at terrifying velocity. It was simply too dangerous to be allowed to continue competing, so it was retired!
Some fun info from Adam Savage about the development and lifecycle of Blendo: https://www.youtube.com/watch?v=0i4dkb5w2Lg
In modern Battlebots, it would be practically useless. Full-body spinners have so many drawbacks, and even when they do manage to land good hits they’re just as likely to hurt themselves.
Blendo was amazing at the time, but the meta has evolved so much since then.
The rules of battlebots lend themselves to wedge bots, unfortunately. Can’t shoot, tangle, or electrocute, for example.
There was one, Depth Charge, that moved by spinning really fucking fast, and would destroy the arena, which was fucking rad.
Thanks for filling up my afternoon