Note: The following names are unofficial.
Beacon Throwers- They just stand rooted to their spots and throw beacons forwards. 
(Crash 1- lab coat version.)
(The Wrath of Cortex- lab coat and black suit version, both with shades.)

Electrified- Charged with electricity, they run against Crash if he gets near them. They're immune to normal attacks, but they can be pushed into hazards when their electricity is off. 
(Crash 1- normal version.)
(Crash 2- Jet-Pack version.)

Flame Throwers- They hang from the ceiling and fire a flamethrower around (Crash 2/XS).

Hunters- Dressed in hunter garments, they shoot slow-moving bullets from their rifles (Crash 2).

Block Lifters- They're dressed in Eskimo outfits and are always found in pairs in Polar levels. They lift blocks up and drop them after a short time, trying to prevent Crash and Polar from progressing. (Crash 2)

Hammering- They're dressed in blue overalls with a red shirt and hat. They frantically smash the ground with their hammers when Crash gets near them (Crash 2).

Shielded- They try to push Crash off of cliffs by using a big shield, unless Crash repays the favour. These are the only Lab Assistants to have blond hair. (Found in Crash 2- lab coat version/The Wrath of Cortex- black suit version with shades).

Knights- Dressed as knights, they try to carry a heavy sword, but can only lift it for a while, which makes them spin. (Crash 3)

Frogs- When these frogs kiss Crash, they turn into their true form- a prince Lab Assistant. (Crash 3).

Wizards- They cast spells at Crash, which transforms him into a different creature. 
(Crash 3- they turn Crash into a frog. In the NTSC versions, they have 1 hit point. In the PAL version, they have 2.)
(The Wrath of Cortex- these have 1 hit point and turn Crash into a bat.)

Double Headers- Large buff Lab Assistants with two heads who stay in their spot, swinging their two clubs one at a time. Their only vulnerable points are their heads. (Crash 3)
Note: In the Japanese version of Crash 3, these Lab Assistants only have a single head.

Swamp Assistants- They're just regular Lab Assistants that lurk from dark swamp waters (Crash 3).

Chinese Assistants- These can be lifting iron, practicing martial arts, or just carrying water buckets. (Crash 3)

Boat Pirates- They row their boat around and around (Crash 3)

Anchor Pirates- They spin an anchor in circles around them. (Crash 3)

Ancient Roman Assistants- These crowded the stadium in Crash's battle against Tiny Tiger, in Ancient Rome.

Racing Assistants- They drive blue cars in which to race Crash (Crash 3)

Coffin Mummies- They hop around in their coffins, and try to grab Crash if he breaks the coffins (Crash 3/N-Tranced)

Spiked Mummies- They hop around in halved coffins, covered in spikes (Crash 3/N-Tranced)

Ancient Egyptians (Lever)- These pull a lever that causes a big block to fall from the ceiling (Crash 3/N-Tranced)

Ancient Egyptians (Flamethrower)- They use flamethrowers to sweep the air with flames, left and right (Crash 3).

Ancient Egyptians (Shield)- Defensive only, these Lab Assistants try to prevent Crash from passing through, by using an enormous shield. Their legs are their only vulnerable spots (Crash 3/N-Tranced)

Arabian Swordsmen- The ones wearing a red turban walk back and forward. When walking back, they swing their swords. The ones wearing a black turban stand in the same spot, and throw swords forwards (Crash 3).

Magic Carpet Assistants- They fly around in a small carpet and try to put Crash in a vase. (Crash 3/N-Tranced)

Genies- These green Genie Assistants fly around in Arabia (N-Tranced).

Plane Pilots- They pilot small planes and shoot at Crash or Coco (Crash 3/XS).

UFO Pilots- Some hover close to the ground and just stand still. Some hover high and try to abduct Crash (Crash 3/XS).

Ski Assistants- These just ski in the snow from the sides (The Wrath of Cortex).

Boxer Knights- Dressed in armour and boxers, they move sideways and try to prevent Crash's passage with a shield (The Wrath of Cortex).

Toxic Senders- They stand in the same spot, whilst expelling presumably toxic substances from their deposits. (The Wrath of Cortex).

Ninjas- They appear out of thin air and throw shuriken stars at Coco. They quickly disappear after it. (The Wrath of Cortex)

Gong Beaters- These use clubs to beat big Chinese gongs for no reason, hurting Coco if she gets near them. (The Wrath of Cortex).

Underwater Assistants- Some wear an underwater suit that is attached to an oxygen tube, and move up and down very slowly, shooting projectiles every once in a while. Others don't wear suits and just remain in the same spot, as if they were sitting. These too shoot projectiles. (The Wrath of Cortex).

Robotic Droids- These have a very robotic appearance and shoot slow lasers every once in a while (The Wrath of Cortex).

Funky Assistant- This unique Lab Assistant is found in The WoC's ending credits. He has an afro, wears old disco clothes and jiggles around with Crash. (The Wrath of Cortex).

Tribesmen (Blowgun)- They shoot darts from a blowgun (XS).

Tribesmen (Spears)- They stand in the same place, throwing spears (N-Tranced)

Tribesmen (Fire)- They spit out fire every once in a while (N-Tranced)

Walking Assistants- The most basic of all, these just walk back and forth. (Fusion)

Walking Flame Throwers- These walk around with a flamethrower. (Fusion)

Ray Gun Assistants- They hover in the same spot with a hoverpack, shooting projectiles from their ray guns.

Mini-Game Hosts- Lab Assistants sometimes appear as hosts in a few mini-games (Boom, Bang!).

The Lab Assistants make a small cameo in Crash Nitro Kart, in the form of statues in Tiny Temple.