Warhammer 40,000: Dawn of War: Winter Assault/Imperial Guard

Imperial Guardsman
The basic Imperial Guard infantry unit, Guardsmen are sort of weak but also cheap and numerous. They can be upgraded with grenade launchers or plasma guns; the latter has higher damage but the former will disrupt enemy infantry. However make sure you don't support melee units with grenade launchers or you'll find them all over your screen as well. When you have Guardsmen, it's better to keep them behind your Marines - they have low morale and health so they just end up being broken and whittled away in short order if in front. From the back, they can provide a decent amount of supporting fire to your main force.
 * Class: Infantry
 * Role: Ranged anti-infantry

Leman Russ
A basic "workhorse" tank that is somewhat effective against everything. The battle cannon has very long range, decent vehicle/building damage and lots of infantry disruption power. The heavy bolters will mow down infantry that gets closer. If the enemy has mostly anti-infantry weapons, spearhead with this and follow with infantry, they will hardly scratch it. When facing anti-tank weaponry, you may want to keep these way back and utilize the huge range of the main cannon.
 * Class: Vehicle
 * Role: Main battle tank