Fallout: New Vegas Perks

General information
Unlike Fallout 3, in Fallout: New Vegas you gain perks every two levels. To counter how easy it was to max out the player's skills in Fallout 3, most of the skill-boosting perks from Fallout 3 have been removed or replaced. There are 88 regular perks, 8 companion perks, 16 challenge perks and other unknown amount of special perks.

Companion perks, as their name would suggest, can only be obtained by recruiting Companions. The related perks are only in effect while the requisite Companion is following you: for example, Enhanced Sensors is only in effect while the Courier is accompanied by ED-E.

Challenge perks can be unlocked as well by fulfilling certain requirements. Challenge tasks can be accessed from the Pip-Boy menu; on the 'Misc.' page, accessible from the 'Data' section. Most of the perks obtained this way are related to the skill or task that was completed to earn it. For example, Set Lasers for Fun increases the odds of scoring Critical Hits with laser-based energy weapons; to earn the perk, a player must score a total of 64 critical hits with laser weapons over the course of their game. Additionally, some challenge perks have multiple ranks or more than one version, which 'level up' as the player continues adding to its requisite challenge task.

Special perks are simply those that do not fit into any of the above labels. Special perks can be obtained as quest rewards, from surgical implants, or some other source not previously mentioned.

Note that Companion perks, Challenge perks, and Special perks do not count towards your Perk Rate: you still get 1 perk every two levels, regardless of how many perks were picked up from other sources.

Companion perks
Fallout: New Vegas is not the first Fallout game to introduce the concept of companions having perks, but is the first to have perks that affect the party as a whole.

Special perks
Implant perks are limited to the amount of your endurance statistic. The Endurance implant is essentially "Free" since it costs 1 endurance point but adds a point.