I've had a few in my time:
Rover 825 Sterling, bought for £200, knackered by a local garage for £700 and paid out on their insurance £1,600
Rover 827: Advertised for £1,000 in Auto Trader, had a screen sticker for £2,000. I agreed to pay the £1,000 so they took me to the bank for the cash and by the time I got back the lot manager said the price was £1,250
I walked and they came chasing after me, as I'd walked off the lot I said the price was now £850. I drove it away for that ;D
Pug 306, (basic 4 door one), bought on a whim for £75, ran for a year, tyres were £75, bits and bobs to service it £75, back then a years road tax was £75 and I sold it for ..... Yep! £75!
Jaguar Series III 2.8 - Advertised for £1,600, then re-advertised for £1,000. It went down to £850 and I bought it for £250! The seller called me a f*cking burglar
The current 7 Series 728i, on Ebay bidding was at £550, he wanted a grand for it and I knocked him down to £650.
And the moral of this? Don't negotiate with me as you'll always come worse off ;D ;D