Best car, hmm, hard choice, my Laguna II Privilege was lovely, but the turbo blew up (Renault replaced it, which was nice as I was well over the service interval), went through tyres like there was no tomorrow, having to pull over onto the hard shoulder to "reboot" the car and at £150ish each, was a major drain on my finances. Oh and the headlight washers were tempremental, though the windscreen ones were fantastic, and brilliant at stopping tailgaters! So all in all, maybe not that car...
My 205 GRD I had at uni was great fun, nothing wrong, but a tyre blew (or something) on a bend and sent me careering along a fence and up a pole which broke two of my ribs and left me upside down in a ditch, but apart from that it was a lovely car!
My girlfriend will dissagree (she loved my Meganne that I got after the Laguna II) but I have to say my current Xantia estate is fantastic.
Massive carrying load, lovely drive (now that I've changed the spheres) practically indestructable engine (my previous xantia survived it's engine being filled with water

, and my current one had a cambelt snap a week before I was going to get it replaced) great fuel economy, fun albeit frustrating at times to work on, can run on 100% SVO when the weather gets a bit warmer. Shed loads of oomph, considering it's size and age, it pulls away faster than my mum's Xsara 2.0HDi (surely 2bhp can't make that much difference?)
What more could I ask from a car?
Worst car: 1.4 Astra estate back in 97 that I got stuck with as a "company car" which was supposed to be used for carting PC's around in but as we had a transit for that, was a bit pointless, and I was paying extra tax on the horrible thing!
It would get 40mpg at times however, but that was mainly due to the ECU starving the engine of fuel on the motorway (yes, it would try and stall!) while Vauxhall claimed there was no problem.
Left the job because they wouldn't let me use my own car, and got myself my first Xantia.