Worst: a summer research program in Pittsburgh.. not just because I don't like Pittsburgh

but because I was put into a lab whose research didn't interest me at all, and I didn't have the skills necessary to do anything productive.
I also worked in an
a la carte restaurant on campus in college, but never during the summer. For a while I was always stuck at the "Asian" section which meant deep-frying things and cooking things in a wok. It got painfully warm in the late spring and early fall. I was always covered in this layer of oil droplets by the time my shift was done, it was gross. Not that the other stations were much better.. the giant vat of mayo at the sub station grossed me out, and heaven forbid I got put on dish washing duty.
Best: I worked in Research and Development where my mom works one summer, a company that makes big industrial size mixers (for food production, pharmaceuticals, etc). My primary project was helping to test "gear boxes" (the part that links the motor to the mixer shaft) that probably weighed almost a ton. I tested temperature, noise, vibration, gear contact patterns, etc. Keep in mind I have NO engineering or mechanical experience WHATSOEVER. When my supervisor went on vacation, I was put in charge of testing these things and making sure they were safe to go out to the customers.

I was even invited to important meetings and stuff, where I was the only female. It was a blast!
Also, while not during the summer, I spent a year working early mornings (6-10am) at Macy's on the dock, unloading the trucks and unpacking all the clothes and stuff that came in. It was neat to see all the newest items! Come to think of it, I'm not sure why I liked that job so much, lol.. it was very repetitive and meant 4 hours of standing on cement most days. I guess it's just because I knew it was my last paid-by-the-hour, manual labor type job EVER.