Mobil 1 works fine but it's overpriced. I prefer to use Shell Rotella T Synthetic - it's great oil, has no friction modifiers to make wet clutches slip, and.... Wal-Mart sells it for $12.84 a gallon! No adverse effects on shifting either.
If I'm gonna use a petroleum oil I prefer Shell Rotella T, Mobil Delvac or Chevron Delo (about $6/gallon). These are all commercial grade "heavy duty" 15W-40 oils that are perfect for Motorcycle use in bikes that use a *W-40 oil - if yours needs a *W-50 oil (Harleys?) you might need to look elsewhere though.
Another note on synthetics - there are VERY few "true" synthetics on the market any more, most oils labeled synthetic (including the Rotella I use) are really "Group III" oils, which are actually very highly refined petroleum based oils. They perform almost as well as true synthetics but cost the manufacturers half as much to produce (although no one lowered their prices after switching to these formulations, go figure). If it matters to you, the only true synthetic oils I know of any more are Amsoil, and Motul makes a few formulations. I also hear Mobil Delvac 1 is "real", but this is not confirmed.
http://motorcycleinfo.calsci.com/Oils1.html