Captain Sicarius

During deployment, choose one friendly Ultramarines Tactical Squad.  It gains one of the following special rules for the duration of the battle: Counter-attack, Infiltrate, Scout, or Tank Hunters.

If Captain Sicarius is alive and on the battlefield, you gain +1 to your Reserve Rolls

When choosing an army, all models in the same Detachment or Formation must be drawn from the same Chapter.  If a unit's datasheet contains a Chapter in brackets after the Chapter Tactics special rule - for example, "Chapter Tactics (Ultramarines)" - the unit must always be drawn from this Chapter, and therefore cannot be included in a Detachment or Formation with any units that are drawn from other Chapters. All models drawn from a given Chapter benefit from that Chapter's Special Rule. If a unit contains models drawn from two different Chapters, it counts as from neither Chapter, and thus benefits from neither Chapter Tactic.

Independent characters can join other units.  They cannot, however, join units that contain vehicles or Monstrous Creatures.  They can join other Independent Characters, though, to form a powerful multi-character unit!  Independent Characters pass Look Out, Sir rolls on a 2+. A unit that contains one or more Independent Characters does not need a double 1 to Regroup if reduced to below 25% of its starting numbres, but instead tests as if it had at least 25% remaining.

Full details in BRB. Rule too long to copy verbatim.

In a turn in which a model with this special rule charges into combat, it adds +1 to its Strength characteristic until the end of the Assault phase. A model that has made a disordered charge that turn receives no benefit from Furious Charge.

A unit that contains at least one model with this special rule automatically passes Fear and Regroup tests. When it Regroups, the unit does not make the 3" Regroup move, but can instead move, shoot (or Run) and declare charges normally in that turn. Furthermore, if a unit containing one or more models with this special rule is caught by a Sweeping Advance, they are not destroyed, but remain locked in combat instead.

When a model with this special rule suffers an unsaved Wound, it can make a special Feel No Pain roll to avoid being wounded (this is not a saving throw and so can be used against attacks that state that 'no saves of any kind are allowed', for example those inflicted by Perils of the Warp).

Feel No Pain saves may not be taken against Destroyer attacks or against unsaved Wounds that have the Instant Death special rule.

Roll a D6 each time an unsaved Wound is suffered. On a 4 or less, you must take the Wound as normal. On a 5+, the unsaved  Wound is discounted - treat it as having been saved.

If a unit has the Feel No Pain special rule with a number in brackets afterwards -Feel No Pain (6+), for example - then the number in brackets is the D6 result needed to discount the Wound.