Well, I had a few that I really liked. Top of them all was the Psyclone by Nitrous Karts. I have very little information on the company but that kart was just awesome.
Here are a few pictures of karts I thought looked and handled well.
The pictures, one of these is a Yerf-Dog which we beefed up and stuck a 10hp Tecumseh on, a Brister Concept Kart, Ken-Bar with a beefy engine, and a Yellow-Jacket by Avenger Karts.