The most commonly used AAS in medicine are testosterone and its various esters (but most commonly testosterone undecanoate , testosterone enanthate , testosterone cypionate , and testosterone propionate ),  nandrolone esters (most commonly nandrolone decanoate and nandrolone phenylpropionate ), stanozolol , and metandienone (methandrostenolone).  Others also available and used commonly but to a lesser extent include methyltestosterone , oxandrolone , mesterolone , and oxymetholone , as well as drostanolone propionate , metenolone (methylandrostenolone), and fluoxymesterone .  Dihydrotestosterone (DHT; androstanolone, stanolone) and its esters are also notable, although they are not widely used in medicine.  Boldenone undecylenate and trenbolone acetate are used in veterinary medicine . 
Results wise, users should expect extreme strength increases and weight gain in a relatively short 2-4 week period. Weight gain upwards of 20lbs in 4 weeks is not unheard of with this incredibly potent compound. Although subcutaneous water gain would be minimal, intramuscular water retention should be expected. This is due to inhibition of 11b-hydroxylase and build-up of mineralcorticoids which encourage salt and water retention within the muscles. The most obvious physical effects will be improved vascularity, aggressive muscular pumps, and oily skin.
While methyldrostanolone can stack well with most other steroids, it should never be stacked with another methylated (17aa) steroid.