I've gotten a few odd things here and there, like a Honda Civic. Most recently from my HLEs I've had a G6 (which was really an upgrade to Standard), a couple of Kia Optimas (but they had the Sirius active) and an upgrade to a Camry.

It's highly unlikely you'd get a Mazda 6 anymore. They need to change that description. Only 2008 and earlier Mazda 6 was midsize. The newer one is much bigger and when they have them (I've never gotten one) it's apparently classed as Full.

What you get is going to vary some by location, though, and may vary even more if it's a franchise location and not corporate owned.