Someone changing their fighting style for a fight.
Obvious two would be Condit and Guida.
You can have a gameplan. "Go for the takedown, go for submissions" etc. but you're a fighter who believes in his abilities. If you then completley change from an exciting fighting style to a boring one just for the win, I hate that as a fan. I was a Guida fan before that fight. His relentless wrestling style defined him, but now I see him as a strategist who doesnt care about having a good fight. My favourite fighters are fight of the night fighters.
Also, people who leave it too late to expload. Wanderlei left it until the last 20 seconds of the Franklin fight to go for it. I'd prefer to be knocked out in the 5th when I'm down on the cards than lose by clean decision. As sooon as the 5th bell goes, throw until you get KOed or KO your opponent.