Being a consultant means traveling from time to time (or all the time).  Since May, I've been traveling to Boston on a weekly basis and I've had a variety of cars.  Oddly enough, my favorite car has been a Hyundai; they've really come a long way.  Here's my list of rental car reviews, ranked by preference.

1. Hyundai Elantra *****.  By a close margin, this has been the best rental I've had.  I've gotten these twice and each time, it was a pleasant surprise (although the second time, it was because it smelled like the previous driver was delivering pizza in it all week).  To begin with, Elantras have perhaps one of the best headrests I've personally used.  It moves up and down like most headrests, but unlike others that just tilt forward, it actually slides forward.  Perfect seating posture for me.  The fit and finish on the interior is excellent with very rich feeling materials and soft plastics.  Driving dynamics were so much better than anything I expected.  Sure, you're not going to be autocrossing in one of these guys, but it handles nicely enough for commuting and the suspension is great when it comes to absorbing bumps.  The transmission also does a good job and gear hunting is relatively minimal.  To top it all off, I was able to plug in my Sansa Clip using a USB cable and the radio automatically recognized it and loaded my play lists.  Awesome!  The radio controls actually control the MP3 player.  Finally, this has been the only car that I've had with auto down and up windows (great for toll booths).
2. Ford Mustang ****1/2.  I have to admit, this car was: 1) incredibly uncomfortable, 2) hard to find a good seating position in, 3) difficult to get in and out of, 4) had terrible button/control layouts in the center stack, had those silly Ford light controls (on a knob...).  And yet, despite all of that, it's a great rental car because you just feel like such a badass driving one.  I'd never buy one myself, but it's great fun for a rental.  That said, from the driver's seat, I swear, it feels like you're driving a boat; the thing feels huge.  The V6 engine also seems a bit underwhelming considering the sporting nature of the vehicle.  While the Elantra wins hands down in terms of ergonomics, build quality, and fit-and-finish, the Mustang makes up for its shortcomings by being badass. 
3. Chevy Impala ***.  The Impala was mostly a forgettable vehicle.  The fit-and-finish were certainly nice enough, but the seat was flat as a board and difficult to get comfortable in.  It's ony ranked this high because the other vehicles are so terrible.  Truth be told, if I had one of these as a rental?  I'd probably ask for a downgrade to an Elantra instead.
4. Saturn Vue **1/2.  I just had this one last week.  Like many American cars I've driven, the Vue suffers from terrible steering feel.  The wheel feels very loose and the steering effort seems to be way too light for my tastes with a lot of play on-center.  Despite the big exterior size, its interior size seemed underwhelming.  Speaking of underwhelming, the engine was clearly working overtime to move the mass of the Vue; it felt lethargic and the transmission was constantly hunting for gears.  If I were in the market for this type of vehicle, I'd probably go with a Rogue instead.  Overall, an underwhelming vehicle.
5. Subaru Forrester **.  The Forrester has some redeemig qualities like having AWD, which would be great in the winter, and a spacious interior.  Aside from the chintzy, cheap looking/feeling, plasticky interior, there's not much to hate...but then again, there's not much to love either.  On top of all that, you're driving a station wagon.  It doesn't get much lamer than that :P  Oh yeah, the engine was grossly underpowered.
6. Toyota Corolla *1/2.  This was the first time I'd driven a Toyota Corolla and to be honest, I don't get it.  I was expecting so much more from this car, but it was so disappointing in every respect from the cheap, dark, dingy interior to the forgettable...everyting.  If you're in the market for one of these, the Elantra seems like it would be a much better buy.
7. Nissan Versa *.  Okay, I'll admit: I'm a Nissan guy.  My mom had a Sentra and then a Maxima.  My wife drives a Murano and I drive a Frontier.  If I had the extra money, I'd by a 370z and a G37x and switch them up for my daily commute (if I had one).  But there is nothing redeeming about the Versa.  The interior was not only dingy, it looked positively industrial and completely uninviting.  Like the Corolla, it was mostly a forgettable car.  If I were in this market segment, I'd probably get a Hyundai Accent or a Kia Forte.
8. Kia Rondo *.  Maybe I'm just holding it against this Rondo, but the one I have this week is dirty and stained inside.  If I had the patience, I probably would have asked to trade to an Elantra.  Aside from that, being a tall wagon, it looks particularlly lame.  Its one redeeming quality is that its A/C is super frigid.
9. Dodge Caliber 0*.  Lame. Terrible.  DO NOT WANT.
10. Pontiac G6 -1*.  Perhaps the Pontiac doesn't deserve this hate, but the week that I had it, it was basically pouring every day of the week.  Unfortunately for me, the key fob was broken and I wasn't able to remotely open the door.  This lead me to discover that the G6 didn't have a very basic feature: the ability to unlock all of the doors by double turning the key in the driver side door (bonus level of suck: no key hole on the passesnger side).  This made it extra hard to get my stuff in and out of the car...while it was pouring.  I can't figure why they wouldn't have this very basic feature, but it was a terrible week without it as I constantly had to unlock the rear door from the inside.

This post was partially inspired by Autoblog's spyshots of the upcoming Sonata (another very nice rental).  Hyundai has seriously come a long way since my '98 Accent.  Hopefully, the Consulting Gods will look kindly upon you the next time you have to travel for business (and rent economy) and bless you with an Elantra!