The best

Woah! This is a very broad field we're looking at!

My first reaction is go Lexus - A quick search on Cars dotcom yielded 49 cars under $10k with less than 100k miles, all from 2006 up. In particular there are some beautiful ES350s there.

Adding Toyota to the search added another 476 cars.

If you are looking for a vehicle that will last a long time and that has reliability & durability / Materials & workmanship / Fuel economy, then I say look at Toyota/Lexus. Toyota's two brands lead the field in these characteristics.

Please provide more input on what your needs are. As is you've narrowed the field to about 50% of all vehicles available on the market. How long is your commute? Do you enjoy driving? Will you routinely have passengers in the car or carry cargo? Will this be a road trip vehicle for the family, or just a commuter car?