Question: After Luke discovers R2-D2 in the desert on Tatoine, he says "Sandpeople, or worse." What is "or worse"?
Answer: Krayt Dragons. They're what Obi-Wan mimicks to scare the Sand People away. See http://en.wikipedia.org/wiki/Krayt_dragon.
Twotall
I want to add that Obi-Wan's scream had been replaced twice in special editions. The original audio sounds like it could've been from a dragon for sure, but not the updated ones.
Rassdyt