acually anything 4x4 500 and over i think is good, but like others have said you can do it with any quad. my dads friend stores his polaris sportsman 800 with efi at our house and i can do wheelies without even trying that thing will come right off the ground easy

 

Wheelie's are the easiest on the following machines in this order----
Outty 800/Outty 650- simply give it gas and the front will come up easily.
BF 750i- almost just as easy
BF 650i- very easy
Polaris 800 efi -same as above
Prairie 700- a little more body english required but not much
Grizz 660 - body english required
KQ 700- due to it's low end lag wheelies are harder but they have a sweet spot where they are easy as well.

The key to great wheelies is power--- V-twin power. The Outty 800 has the most right now so it can wheelie the easiest.