the best collabs in my opinion were:

1. Deftones with Max Cavalera: Head Up

2.Max Cavalera with Chino and Grady: Pain

3.Seplutura with Jon Davis from Korn: Rattamahatta

4. that one song that S.O.A.D did with Wu-Tang

5. Down (since that whole band is basically a big collaboration.)

and thats pretty much it since most collaborations suck balls.