Laurifer Gladiator

 is an unmarked quest in Fallout: New Vegas.

Quick walkthrough
Visit The Fort (after unlocking it) and talk to Otho about fighting in the Legion Arena. You will need to fight three different round of prisoners from the Legion. After beating all these three rounds, you will get a lot of Legion fame.

Detailed walkthrough
After gaining access to The Fort, you will need to find a Legion soldier named Otho. He can be found in the upper section of The Fort right outside the Legion arena. You will then need to tell him that you are wanting to fight in the arena. Once inside the arena, you will only be limited to use a Machete and a Gladiator armor to fight against your opponent as all your equipment is removed from your inventory before a round begins. There are three rounds of enemies that you will need to beat:

After beating an opponent in a round, you will need to talk again with Otho to begin the next round. After beating all the three rounds, Otho will say that nothing would be a challenge for the player, so he will stop giving prisoners to fight against you in the arena. You will also receive a lot of Legion fame.

Behind the scenes
Laurifer gladiator loosely translates from Latin as "victorious gladiator".

Bugs

 * After fighting against the two slaves, you can put your holdout weapons into their inventory. If you immediatly start another round in the arena (against Sergeant Andrews) before the slave's bodies disappear, you can get your weapons from the slave's inventory and fight him with your holdout weapons. This can also be done to fight against Ranger Stella.