Some of the patrol rangers have reported that Oliver's power armor heavy troopers are starting to reinforce the front lines. They have the best equipment the NCR can get its hands on, power armor salvaged from our war with the Brotherhood. Techs strip out the joint servos so you don't need special training to wear it. It feels like you're carrying a brahmin on your back, but it can take a heck of a lot of punishment.
Clad in NCR salvaged power armor and armed with heavy weaponry, these elite troopers are some of the deadliest soldiers the NCR has at their disposal, second only to the Veteran Rangers of the NCR Rangers. General Lee Oliver has very high faith in his shock-troopers, and seems almost oblivious to how ineffective the power armor makes them in close quarters. Under General Oliver's command, Rangers are regularly thrown to the sidelines or used as cannon fodder in favor of the heavy troopers, to the point that Ranger Chief Hanlon is actively subverting NCR Intelligence out of spite.
NCR heavy troopers begin to appear after the player either activates or destroys the Securitron army in Mr. House's secret bunker underneath The Fort, or when the PC reaches a medium-high level. They are usually stationed in pairs. Generally Heavy troopers do not respawn if killed.
A pair of heavy troopers will replace the regular NCR trooper squad stationed at the 188 Trading Post.
A pair of heavy troopers will also replace the NCR MPs at Camp Forlorn Hope when the player progresses to a certain time in the main quest line.
Heavy troopers can also be found guarding the Hoover Dam Visitor Center regardless of the player's progression in the main quest line.
If the player is declared a terrorist by the NCR, a squad of NCR Rangers will be dispatched to kill the player. After the most recent patch, this hit squad may include an NCR Heavy Trooper if the player is at a high level.
NCR heavy troopers play a role in the final battle for Hoover Dam, especially if the player sides with a non-NCR faction.
If the player sides with Mr. House or Yes Man, a pair of NCR Heavy Troopers can be found guarding the entrance to the Hoover Dam Control Room containing the control terminal which House/Yes Man wants the player to hack. These two Heavy Troopers have abnormally low health, having only 90 hit points each. If the Heavy Troopers catch the player entering the control room, it will turn them and the rest of the NCR soldiers at Hoover Dam hostile towards the player.
If the player sides with Caesar's Legion, then a group of 6 NCR Heavy Troopers will fight alongside General Oliver as his bodyguards in the final battle, serving as the "final boss" of the game.