I used to work for a rental car company. Driven just about everything they carried up to 2010. One thing from personal experience, VWs suck in a rental fleet. Have to have specialized tools, which most companies don't have, oil filters are a pain to get to, lug bolts instead of lug nuts make for an unpleasant surprise the first time you take a tire off one.
Impalas are decent, and pretty reliable. Hyundais and Kias are both pretty good, especially newer ones.
And to the people bashing the Cobalt, as an SS/SC driver,
