Tarpit

In 40K terminology, a Tarpit is a big blob of expendable infantry intended to be a giant pain in the ass and functionally a living wall designed to slow enemies down and keep foes tied up by either assaulting them or act as a wall. Ideally capable of being placed in cover, almost every faction in the the 41st Millenium is capable of fielding some unit or another that serves this purpose. Some are especially good at it, whilst others are simply mediocre at it.

Tarpit Units By Army

Below is a brief list of some classic Tarpit units favored by various factions in the 40K universe.

Imperial Guard

• Conscript Platoon - 20+ Models for dirt cheap. Do the math.
• Regular Guardsmen - While not as cheap as conscripts, they can still make efficient tarpit units if you send out your non-kitted guys.

Chaos Daemons

• Nurglings - Gets into close-combat and keeps enemies tied up for half a game or longer.

Inquisition

• Inducted Guardsman Squad - still not expensive.

Tau

• Kroot Carnivores - Inexpensive infiltrating models at 7 points each. Hell of an area denial unit.
• Gue'vesa Auxillaries - Even less expensive and can't infiltrate but shooty and with decent wargear options.

Tyranids

• Ripper Swarm - vulnerable to Instant Death and blast templates, but will tie foes up for round after round if they get close.
• Gaunts - Cheap and effective mass unit.

Orks

• Nearly every type of cheap yet numerous Ork Boy squad (Sluggas, shootas...etc).
• Gretchin - Dies like bitches to nearly everything, but numerous, can hold objectives, dirt-cheap, and can actually shoot better than most Ork boyz.

Necrons

• Scarab Swarm - Vulnerable to instant death/blast temps, but cheap, can get a 2+ save with turbo and a fuckton of wounds, unless you get attacked with ID or blast templates.
• Warriors - When DON'T you have a metric fuckton of warriors?

Marines

Factions like the Space Marines, Chaos Space Marines, and Grey Knights do not to have any real tarpits, due to the fact that most of their infantry squads are small and they're all fairly expensive compared to other factions.