Here are a few rules that came up in the last game.
JJ typing, Impassable Terrain 40k6 pg 90
Models cannot enter, cross or move into or through impassable terrain -- they must go around.
Context: Shawn asked what models can go into impassable terrain. Informed none. Except Skimmers 40k6 pg 83 and Flyers 40k6 pg 80. Skimmers have to take a dangerous terrain check if they end their movement in impassable terrain. [Update] Thanks to Allan's comment reminding me that Skyborne under Jump Units pg 47, Jet Pack Units pg 47 can also land on Impassable Terrain. It is treated as dangerous terrain. Provided Shawn the incorrect information.
Eldar Warlord, 6th ed Eldar Codex pg 26
No mention that the Avatar of Khaine has to be the Warlord if its in primary detachment. Unlike Asurman as Shawn mentioned on pg 56: If your primary detachment includes Asurman, he must be your Warlord.
Context: Shawn mentioned that his Spiritseer is his Warlord. I thought that the Avatar had to the Warlord if he was taken. Guess I was wrong. [Update] Again thanks to Allan for reminding me of pg 111 This is always the HQ choice character with the highest Leadership. I wasn't thinking about Leadership regarding the Avatar being the Warlord. Just that in Avatars description it said if he was taken in your primary detachment he had to the Warlord. It doesn't state that in the description in the 6th ed Eldar Codex.
Moving Walkers 40k6 pg 84
Difficult terrain affects Walkers just as it does Infantry, and only counts as dangerous terrain if it would do so for Infantry.
Context: Shawn asked if War Walkers had to roll 2d6 to determine how far they moved. Orikan and C'tan with Writhing Worldscape powers were in effect. Informed yes.