The high-pitched sound the blasters make? Burtt came up with that. Chewbacca's voice? Burtt created it by recording a moaning walrus and layering it with some other animal sounds. On top of this, he didn't just design R2-D2's sounds but actually performed most of them himself. That's right -- he is R2-D2.
But his work didn't stop with Star Wars. He also personally designed E.T.'s voice and personally performed the adorable voice of WALL-E. Yeah, he's WALL-E as well.
For the sake of time, we're going to skip over talking about the whip and boulder sounds from Indiana Jones (he made those, presumably with his sizable wang) and move on to a signature sound effect that is in almost every modern action and adventure film: the Wilhelm scream. It's a clip of a man screaming that's been used over 200 films:
Burtt discovered it. Burtt named it. Burtt is the father of the Wilhelm scream which he stumbled across on a studio reel labeled "Man being eaten by alligator" and made famous.
We would keep talking about that, but it turns out there's one more Burtt Star Wars sound we should mention: the lightsaber sound. The electric "unsheathing" sound when the beams emerge, the humming and clashing of the fights -- sounds that every kid can make with his mouth (they kept having to stop Ewan McGregor from making that sound while shooting the scenes in the prequels).
Liam Neeson was constantly breaking character to weep openly in shame.