I’ve been using Sicarius for my last few games up to 1500 points, and I must say he has given my armies a huge variety of tactical decisions!
Of course, he’s got all the benefits of being a Marine Captain plus 2+/4++/FNP and insta-kill, but it’s those extra special rules that make him a frightening opponent.
Surprise Attack almost guarantees that all your reserves hit the table early in the game. The more that reserves make up your strategy, the better the chances of Surprise Attack making an impact. Obvious strategies include Drop Pod assaults, massive air attacks and big outflanking attacks with Scouts or Battle Forged Heroes – more on that later!
Rites of Battle ensures that all your units use Cato’s high Leadership for morale or pinning tests. I find it very rare that this becomes useful considering all Marines already negate Fear, but if your enemy uses a lot of barrage or sniper weapons, then this could become handy.
Battle Forged Heroes gives one of your Tactical Squads Counter-attack, Infiltrate, Scouts or Tank Hunters during deployment. This is by far the most valuable ability available for Cato (and I’d argue for the entire Codex too!). The combination of this plus Surprise Attack allows you to Outflank with a Rhino full of Tactical Marines to pressure the enemy. If you prefer to keep your army on the table from turn 1, you can give them Scouts to make an early dash to better firing positions. If your Marines are already in a Drop Pod, you could give them Tank Hunters and drop them close to enemy armour to act as Sternguard lite. Alternatively they can form deadly defenders with Counter-attack if you manage to sit them on an objective (unfortunately it won’t benefit from Rites of Battle, since Counter-attack uses Leadership and not Morale tests). The possibilities are endless, and since you can change during deployment, you can be flexible too!