My not so scientific approach based on (past/present) favs:
Stand-Up: Mirko Filipović (Kicks) / Vitor Belfort (Hands)
Takedowns: Mark Coleman/Kevin Randalman (both took down Fedor...good enough for me! LOL)
Clinch: Wanderlei Silva
Ground and Pound: Fedor Emelianenko / Mark Kerr (In his prime)
Wrestling/Ground Work: Dan Henderson / Couture (early) / Royce (early)
Submissions: Antonio Rodrigo Nogueira/Royce (early years)
Conditioning: Cummo
Takedown Defense: Chuck Liddell/Mirko Filipović
Heart: Griffin/Bonnar

Overall Toughness: Oleg Taktarov (In his prime, you coulda split his head open w/a pickaxe and he wouldn't have cared. LOL)
Confidence/Attitude: BJ Penn/Brandon Vera (LOL Between the two of them, and their desired conquests....you've got every single weight class covered)