Probably a brand spanking new 486 DX-2 66mhz a long long time ago.
This was at a time when new processors were few and far between, Intel weren't knocking them out at a rate of knots back then and the DX-2 66mhz was for me possibly the first Super processor for home use.
I used 8086, 286,286 etc but the DX-2 was the stuff of dreams, you could only wish to have one and a mate got it. Couldnt believe how fast that sucker was at the time!