I've bought and sold over 20 guitars, and i regret half of them i'd say.
Some of them were pure lemons... some were fantastic looking back, just my playing got in the way!
The biggest 'doh' of mine was selling an ENGL Screamer, but i got it cheap so no worries.
If i ever get into the situation where i'm forced to either sell it's way to me right now or eat, i'll probably starve...