Best:
The TC6.1 I ran 2 years ago handled better than any TC I have ever driven. I am running Xray now and I am sure I will get it to where I like it soon enough.
Off-road wise I left Kyosho and started running Losi this year. The buggy suits my driving style and is tough as nails.
Worst:
When I got into RC I bought a TC3 on the advice of the LHS. This was at a time when the Xray FK105 was out. I could never get the TC3 to drive well.
The winner of worst car goes to the Associated RC8B. It was the worst buggy I have ever driven (along with a friends Durango) and the only buggy that turned like a monster truck. I took it to one big race in the US and sold it immediately after.
-Kane