Almost anything Honda makes. The Foreman lineup is hard to beat. Yamaha Big Bear is also hard to beat and has been around for years. On used quads take a really close look though. They tend to get abused and the prices on a good one won't be much cheaper than a new one. On that Artic Cat 250 I mentioned, with the triple range transmission, you will be able to do alot more than you would think. It helps to get every bit of power out of the motor. If money was not a consideration, I would recommend the Yamaha Grizzley 660, Kawasaki has a new monster 4X4 with about 650 or so cc's and Polaris has a 700 I believe now. Generally most folks do not need anything that powerful, and it has become the Thing, to have the biggest baddest motor. For most of us, it is wasted power and $. But if you got it, buy it. Artic Cat has a new big quad as well. Check out the info, and new line-ups at that web site I lsited. Lots of good info there.
markc