Dude, said with different inflections for slightly different meanings.
Dude, said casually, and a little drawn out, with a smile and a slight nodding of the head. Meaning: That was great! (or awesome, which in So Cal, kind of means the same thing).
Dude, said in a shocking, clipped tone of voice, and quite a bit louder than the above ^^ dude. Meaning: I can’t believe you just did/said/ate that.
Dude, asked as a question. Meaning: are you there/OK?
Dude, said rather quietly, whilst slightly shaking one’s head. Meaning: You should not have done that/said that/gone there.