Blue Spotted Timors are really cool.
Ackies aren't too bad either.
Tegus make awesome pets, and I will be getting one sometime this year.
Just choose whatever you feel you can take care of its entire life. Like stated before, please do your research. Monitors do have huge appetites and love a variety of different things. Also sometimes cage requirements can get costly (substrate, enclosure size, lighting, heating, etc.). So make sure you have the money to get everything for the monitor and fulfill its needs for the rest of its life.