I'd have to say it was my '86 Ford Escort. I feel bad calling it the worst car because it really was a champ and put up with so much abuse. However there is a story why it is the worst:

Driving down the freeway one day I was lightly hitting the steering wheel while listening to a song and the entire wheel popped off in my hand with the wires attached. I showed it to my buddy in the passenger seat and he screamed "Put it back on! Put it back!" So I stuck it back on the steering column and drove back home. I told my dad there was a problem with the Escort and when he asked what I offered to hand him the wheel. I donated that car not too long after.

Here's why I feel bad for the poor thing. My parents bought it for my brother as his first car from a real nice guy who said it had never had any issues. The car looked good and seemed to drive good. However, one day while my brother was driving it the front end basically fell apart from the rest of the car. It turns out the car was in a major wreck and the front subframe had been poorly rebuilt . So the front end was reattached a second time since being built. Front end number 3 came after I had the car for a while, it was a hand-me-down. I wasn't too surprised when the frontend had to be repaired though. Between my brother and I that car had logged more flight time than most people with private pilot licenses. That car loved to fly. If you're ever in Simi Valley you might see parts of a white escort dug into most of the intersections that cross the railroad tracks. Then again we also played Dukes of Hazzard in it and took it through trails that our friends trucks were getting stuck in. Man I miss that car at times.

I have many more wonderful car/truck stories, but that escort was the worst from the get go.