Hormagaunt
Hormagaunts are the Tyranids' basic assault organism (read: tarpit). Equipped with a pair of Scything Talons, their job is to rush into close combat and either slice things into nice small pieces, or keep enemy walkers from moving anywhere. They can be assisted in the former role by the addition of Toxin Sacs or Adrenal Glands, making them even more killy. They can be assisted in the latter option by keeping some Synapse nearby. As they're members of the gaunt genus, they're unsurprisingly most effective when fielded in numbers, though they don't need quite the same numbers termagaunts do. Good for drowning your enemies in poisoned attacks.