Tyranid Termagants are expendable creatures that provide ranged support in engagements. Like most Tyranids, they are fast moving, but this unit has no armour save.
Boyz are likey the most numerous unit in an Ork army. They are proficient in close combat and can overwhelm their opponents with shear numbers. They also have limited shooting ability, but their accuracy leaves a lot to be desired.
The Leman Russ Battle Tank is an iconic, heavily armoured vehicle used by the Imperial Guard. Millions have been built and sent to the front lines, where they provide the Imperial Guard army with powerful anti-infantry and anti-armour capability.
The Archon is a the Supremme Commander in a Dark Eldar army. He is an accomplished close combat fighter, able to defeat even heavily armoured targets with his speed and power.