Goku

If Goku was hit by Buu's Change Beam, i think Goku would be a fighting candy, just like Vegito.
 
Vegito is only a fusion of Goku & Vegeta, nothing more. So i think it is reasonable to believe the same scenario would occur if Goku & Vegeta were hit with the beam, outside of being fused.

I believe Vegeto kept his abilities because of his high ki, even magic beings with ki lower than Buu cannot resist the beam (Dabra). 
If say Monster Carrot or someone used transmutation on Goku, he would keep all his powers, as Vegeto did against Buu.  And as Kid Buu did against Fat Buu when the candy beam was useless (off hand ICR if it is filler, but the point remains)
Since the ki of Buu is around the same as Goku, it should work. 
Certainly if Mystic or Gotenksbuu fired the beam, it would work imo. 
If fat Buu fired the beam, then no I think Goku's ki would allow him to keep his abilities. 
If Kid or Super Buu tried it, idk.  
 
Also interesting to point out, Vegeto breathed just fine as candy, thus proving he does not need oxygen.