Picked up two things from last nights game.
Fear 40k6 pg 35
At the start of each Fight sub-phase, a unit in base contact with one or more models that cause Fear must take a Leadership test (called a Fear test) before any blows are struck.
Context: Dire Avengers assaulted the C'tan. Had Dires roll the Fear test. Succeeded with a 9. Next turn I wondered if the Fear was only once they would never have to roll again. Turns out units fighting Monstrous Creatures or other models with fear have to roll at the start of each fight sub-phase.
Jink 40k6 pg 38
A model with this special rule that has moved in its Movement phase gains a 5+ cover save until the start of its next Movement phase.
Skimmers 40k6 pg 83
Skimmers have the Jink special rule.
Context: Immortals shot at Wave Serpent doing enough to strip its 3 hull points. Because Wave Serpent has the special rule Jink it had a 5+ cover save against the glancing Gauss Blasters.
Side note: Can imagine this useful for Eldar and Tau armies. Save Dark Eldar points from buying Flickerfield. Then again you don't get a cover save against template weapons.