For 10 points give this highest and rarest military honor in ancient Rome, which could be awarded only to a Roman commander who killed the enemy commander in single combat.
Corneilus Cossus in 428 B.C. and Claudius Marcellus in 222 B.C. were the only two men ever to win them--although Roman tradition adds Romulus to the list for his legendary victory over the King of Caenina.  The younger Crassus probably should have won them as well, but Augustus vetoed the award, fearing a potential rival, and it was thereafter abolished.  For 10 points give this highest and rarest military honor in ancient Rome, which could be awarded only to a Roman commander who killed the enemy commander in single combat.
Corneilus Cossus in 428 B.C. and Claudius Marcellus in 222 B.C. were the only two men ever to win them--although Roman tradition adds Romulus to the list for his legendary victory over the King of Caenina.  
Spolia opima or Spoils of Victory