John David Jackson
Guillermo Rigondeaux
Wladimir Klitschko
Bernard Hopkins since about 2002 (exciting in late 90s into the 2001 Trinidad fight.)
Chad Dawson
Adrian Broner
Tim Bradley
Devon Alexander
Winky Wright

The difference is most of these flatliners remain anonymous to the mainstream, but the mainstream insist on paying top dollar for Mayweather's carefully-selected sleep-inducers (Maidana fight excepted).