Giant Killers IMHO must be reasonably affordable, have had an serious impact on the market and/or been outrageously good for the bux. So here are a few...
Speakers: Spendor BC1, Quad 57, Quad 63, LS3/5A, Vandersteen 2, Infinity IRS, Tannoy Concentrics, Wilson WATT
Turntables: Linn Sondek, Goldmund Studio, EMT, Garrard 301, Rega Planer
Phono Cart: Koetsu rosewood, Grado Sig, Grado FT+1, Shure V15, EMT, Decca
Tonearm: Goldmund T3, Morch DP/UP, Rega 300, SME 3/4/5, Sumiko "the arm"
Preamps: Audio Reserch SP6 series, Dyna PAS, Dennesen JC-80, Marantz 7, CAT, Hovland HP-100, Audible Illusions 3
Amps: Marantz 8/9, Mac tubes, Dyna ST-70, Audio Reserch D-79b, Adcom 555
Wires: Monster, Audioquest, Kimber (they made the market for better or worse...)
CD players: Errr...
Regards, Kevin