Perks
A Real Soldier: You're loyalty to the NCR is unmatched. Any NCR troopers near you gain combat bonuses.
Acquired by: Gaining enough NCR loyalty
The Final Frontier: You've explored the Mojave an seen some of the most ugly mother f***ers out there. The best way to kill them: with the biggest bug zapper you can find. You gain a 75% damage increase against mutated creatures with energy weapons.
Acquired by: Level 20, Science and Energy Weapons at 75
Ace of Spades: You hold all the cards. In addition to an 8% critical hit chance you're enemies suffer various bouts of bad luck (guns jamming, dud grenades, etc...).
Acquired by: Level 25, Luck 8
This is just an idea based off FO:Tactics. At some point in the game (or multiple points, either or) you can change your race based off previously used ones: ghouls, talking deathclaw (yes, some talked, look it up), robots, and super mutants. Since most humans are bigots in FO (says a lot), you lose 1 charisma for a race change.