Sausage at Contigo Austin, which is a really cool place to hang out. Simple, home made food done well, good drinks, outdoor dining, inexpensive, great place for you and 6-7 friends.
They make their own mayo and sauerkraut
Burger from Cover 3 - supposedly one of the best in Texas according to Texas Monthly. It was really good, but the waitress kind of screwed up my order. VERY juicy.
The fries were excellent. I would get this with bacon next time.