I've had 30+ cars over the years. I miss my old Colt Galant turbo, it was such a comfortable car to drive long distances, easily cruising down the motorway at a steady 110mph. Selling my first (of two) Toyota Soarer twin turbos to pay the rent was also regrettable, but necessary. I sold it to a mad Irishman whose only sms to me was "f****** fast!", before he fatally crashed it (the car, not him). More recently, my daughters disposed of a BMW 750iL I had sitting around in the south of Spain - they 'gave' it away for about 400€. The deep dish 18 inch BMW alloys alone were worth more than that!
Regret is a strong emotional word. Some of my cars were 'fun' to drive - the M5, and even the Renault 4 I learned to drive in. The one that put the biggest smile on my face was the Alfa Romeo 147 Twin Spark 2.0, simply because it just kept pulling all the way up the rev range! You could not drive it without wanting to pull out and scream past whatever was in front of you!
My current Rover CDTi Tourer rates as one of the most liked. I know I will be sorry when it has to go...