If you want the best practice guitar amp around, I strongly recommend the Roland Micro Cube series. In addition to its rugged good looks and portability, the amp contains a wide variety of sounds that are exceptionally well done thanks to Roland’s COSM amp modeling.
There are a number of clean amps, from the company’s own Jazz clean to a Fender Deluxe Reverb, though the distorted amp models are exceptionally well done, including a classic Marshall stack sound as well as a Mesa Rectifier model. The onboard effects are first rate as well, including tremolo,, chorus, flanging, phasing, reverb, and delay. An auxiliary input is also included so that you may play a CD player or mp3 player through the amp to facilitate practicing. The onboard tuner is short on functions but still very effective.
Easily, the best practice guitar amp on the market today is from the folks at Roland with their Micro Cube practice amp, available in black, red, or white. The pricing is around $150 new, though you can usually get it around $100 used.