Enclave soldier (Fallout 3)

Enclave soldiers are the main infantry of the Enclave, and are the toughest, strongest, fastest and most well-equipped human enemies the Lone Wanderer will face in Fallout 3. Their equipment is superior to even the advanced armor and weapons used by the Brotherhood of Steel. Enclave soldiers benefit from professional military training and communication systems.

Enclave officer
Enclave officers wear standard Enclave officer uniforms and hats. They are armed with plasma pistols, and carry plasma grenades as backup.

Enclave trainee (rank 0)
Enclave trainees can be found at certain Enclave outposts after The Waters of Life, doing push-ups under the supervision of an Enclave officer. Trainees are equipped only with laser pistols; they do not wear helmets, and their power armor is in extremely poor condition.

Enclave soldier (rank 1 & 2)
Regular Enclave soldiers wear Enclave power armor, and are usually armed with laser rifles and laser pistols. On rare occasions, they can also be equipped with flamers or Rippers. They also carry a random chem, like Psycho or Buffout. After downloading Broken Steel, these particular soldiers become rarer (especially at higher difficulty levels and after completing the main questline) compared to Enclave soldiers with Tesla armor or Enclave Hellfire armor.

Enclave Tesla soldier
As their name suggests, these Enclave soldiers wear Tesla armor, and are usually equipped with plasma rifles. They may also carry miniguns, Gatling lasers, or missile launchers.

They become more common at higher levels, and can replace regular soldiers in Vertibird drops. They also appear in fixed locations (such as in front of Alexandria Arms), or as Colonel Autumn's bodyguards. They are considerably tougher compared to regular soldiers, thanks to their superior armor (which is usually at near-top condition, no less) and their tendency to carry heavy weapons more often than other classes of Enclave soldiers.

Enclave Hellfire troopers (Broken Steel)
Enclave Hellfire troopers are a new variant of soldier added by the Broken Steel add-on. They wear Enclave Hellfire armor and are equipped with heavy incinerators. They also carry a plasma pistol as a sidearm.

Enclave soldier (Hellfire armor, Broken Steel)
The Broken Steel add-on also adds regular Enclave soldiers armored in Enclave Hellfire armor. They wield plasma rifles and have the same stats as the Hellfire troopers, but are just called "Enclave soldier" in-game. At the Very Hard difficulty level, they are tied with their Tesla armored comrades in being the most common Enclave soldiers (it seems equally likely to encounter both varieties). This can be a problem for unprepared players, due to their tough armor, hard-hitting plasma rifles, and large amount of health. It does, however, make spare parts for your own Hellfire power armor easier to come by.

Appeareances
These Enclave soldiers appear in Fallout 3. They are also legacy content in Fallout: New Vegas.

Bugs

 * Occasionally Enclave soldiers and Enclave officers found randomly in the Wasteland will appear as friendly to the player. If you speak to them they will either say "Hey there." or "Yeah?" and the only dialog option is "See you later".
 * Tesla armor-wearing Enclave soldiers carrying missile launchers are always initially friendly towards the player. They will only turn hostile if they see the player fighting against other Enclave forces.
 * Sometimes, the shield that blocks a bridge to the north of Project Purity will not be active, and the player can cross right over it. Enclave forces encountered past the shield will initially be friendly to the player.
 * It is possible to see Enclave soldiers before they are supposed to appear in the Wasteland -- even, in some cases, at the very beginning of the game. This seems to occur most often when one plays a save file where the Enclave is present, and then loads a save file where the Enclave hasn't appeared. This can make Enclave soldiers spawn early (usually where Enclave bases would appear late-game).