Here are the ones I've noticed :
Walt - Traits
Krazy 8 - Sandwich crusts as you mentioned
Gus' dealers - The ability to use kids to his advantage. The dealers used the kid on the bike to kill Combo. Walt poisoned Brock to turn Jesse against Gus and set his killing in motion.
Gus - Ruthlessness. He can kill/have people killed with no remorse. He can be seen whistling soon after Todd kills the kid on the bike showing that he can just shrug it off as something that had to be done. He has all of Mikes guys also killed and it doesn't seem to bother him. I think even if he didn't kill Gus he would of went this way anyway.
Jack - I'm not sure about this one. Jack shoots Hank in the head mid-sentence. Walt shoots Jack in the head, mid-sentence.
Walt - other
*Aeroplane crash* - He caused the crash by allowing Jane to die. He kept the eyeball of the teddy bear. Not a trait but interesting.
Gale He ordered Jesse to kill Gale. He kept Gales book even though it was possibly incriminating. Again not a trait but interesting.
Mike Before Mike's demise, Walt would get his drinks a certain way. Mike would always order his drinks with ice which Walt adopted at Hank's some time after dispatching Mike. Also in Felina when he is confronting Elliot, his tone matches Mike's perfectly when mocking Elliot's knife.
I can't think of traits Walt acquired from the following characters :
- Gus' guys in the lab
Perhaps I missed something!
As far as I can remember Jesse only killed Gale and Todd. I don't think you can say that Jesse took any of Gales traits. He became a better chemist but that was probably going to happen anyway. And he killed Todd right before the end of the series so we had no time to see if he took any.
Todd kept the Tarantula the kid on the motorbike was carrying.