I'd go for a short dress (not super short) that has thick straps and is fairly fitted up top, then flares a little at the bottom. A skater dress basically.
www.msfairy.com has the collection of sexy party dresses., plus the website is currently having a sale and is free world wide shipping which is kind of a bonus.
They can be dressed up or down, look good with mostly any jacket and accessories, and look pretty without being too casual or too dressed up. Basically a staple for me haha.
If you going for a Farewell party and if you are a girl I will advise you to wear Short Dresses. You will look beautiful in short skirts and you will grab the whole show at Farewell party.