Tyranid Harridans are huge nightmare creatures that fly above the battlefield, swooping to strike with Bio-Cannon and Crushing Claws. They can also carry Gargoyles, delivering them straight into the heart of the enemy.
The Termite is a tunnelling machine used to transport troops into battle. The premise is similar to deployment via spaceship drop, and the enemy player does not know exactly when, or where the Termite will appear.
Imperial Guard Snipers are excellent for taking out enemy targets of high importance. They can also provide a useful screen to protect against assaults on valuable friendly units.