An Imperial Knight Paladin excels in engagements, where its Chainsword and Shock Lance will make short work of most targets. It is also armed with a Battlecannon for long range support.
The Ordinatus Mars is a gigantic mobile weapon platform employed by the Adeptus Mechanicus. Its Sonic Disruption Cannon has huge range, and will destroy absolutely anything under multiple blast templates. It has Void Shields for protection, but will almost certainly be a priority target for the enemy.
Berzerkers are frenzied close combat monsters who will likely tear apart most oppenents they get to grips with. They have good armour and will not break or flee when the going gets tough.