For some reason I can't throw a Buzz to save my life. But it seems to be an awesome disc for everyone. That would be my reccomendation. I personally perfer a Pro-D Drone.
Maybe a Hawk that seems to be a pretty easy disc to throw.
Well there is the Core (latitude 64) It's a Buzzz killer. The Roc, Millinnium Sentinal (overstable), Panther (good turnover disc), and the Buzzz, but I only like the First runs or the "second first runs"
if he cant throw a comet i have no idea, what is the comet doing when he throws it? is it diving right RHBH or hyzering out to early? if hes turning it over anything stable or overstable will work. if its hyzering out to earily its his form and and no disc will help him there execpt maybe a putter. either way it sounds like he needs work on his form. teach him the X step and tell him to keep the nose flat, outter wing up and keep his elbow high when he comes across his chest. saw a noob with these problems the other day on a local course, gave him some tips on hole 3, by hole 6 he had out drove all his previous longest drives 3 times in a row. he even got up to 250 and parked one by the end of 9. he was maxing out about 120 when i saw him on the first two holes. nice guy though, glad i could help him out.
well it definitely sounds like a form or grip issue, start there before he starts spending cash on discs that wont help. he needs to experiment with different grips till he finds one that works for him and can throw the comet straight consistently. i wish there was a magic disc for beginners but there isn't. once he can start throwing and releasing consistently then we can help him with disc selection, but one type of disc should almost aways land in the same place when thrown the same, so the disc ISN'T the problem its him. search the net and have him try a bunch of grips till he finds one he feels comfortable with, then have him learn how to throw flat and straight with it, for now. good luck.
forehand a warrior or shark , backhand a wasp or element, sorry not on the buzzz or roc bandwagon , if he is new to the sport i would say go with the shark which was the only midrange i used for the first 3 or 4 years i played and they roll:)