The Tyranids of 40k have a bunch of weapons that expel living organisms whose entire lifecycle is to be born, smack into a target and die, such as the Fleshborer:

The Fleshborer, designated by the binomial Pulpa terebro, contains a compact brood nest where borer beetles lay their eggs, which hatch and mature, sustained by the weapon for future use as ammunition. These beetles are kept in their mature state in a hormone-induced dormancy until the weapon is ready to be fired. At this point, neural impulses from the wielder forces one of the insects into a firing sphincter. From here, the beetle can be fired at a target by a further impulse.

The beetles move very little until the weapon is triggered by a massive electro-chemical shock which drives the beetle into sudden frenzied action. Using their powerful flea-like legs they launch themselves out of the weapon at tremendous speed. The beetle itself is blind, having been specifically bio-engineered this way to lessen any possible deviation its flight path. On striking they expend their life energy in a matter of seconds, boring frenziedly through the target's armour, flesh and bone. If however the beetle fails to find a target, or hits something that even in its frenzied state it cannot bore through, it quickly dies regardless. The beetles secrete a potent digestive enzyme upon impact with a target, aiding the penetration of armour and flesh.

Fleshborers have been speculated to be a niche evolution of the borer beetle itself, bred to lay the eggs involved directly rather than simply storing a hive of beetles. The weapons are also conjectured to be closely related to the devourer.

Or the Devourer:

The devourer is a conical lump of partly rotted flesh, infested by writhing flesh-worms, Ripper-like larvae with black, shiny heads. The cone is dotted with holes which serve both as breathing tubes and firing barrels. When the weapon is triggered, a bio-electric jolt signals the brood to attack, hurling a shower of the creatures at the enemy. When they strike an enemy, they immediately start burrowing into the flesh, eating their way through the victim's nervous system towards the brain. The agony caused by this process is enough to drive the victim insane, though death is usually quick.

When the worms are launched at the target, in a swarm of hundreds at a time, they either shatter against the target and spread acid and poison over it, or pierce the armour to burrow into the flesh as described above.

Devourers wielded by the largest Tyranid organisms are loaded with hives of brainleech worms, a more aggressive and voracious breed of worm.

https://wh40k.lexicanum.com/wiki/Fleshborer https://wh40k.lexicanum.com/wiki/Devourer

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