I've had an idea for an interesting scenario of 40K which I have play tested with Marines and Chaos Marines and thought was extremely good fun.
The basic idea is to setup a level on a 6x4 foot board filled with densely packed terran like a city or town etc with lots of building and narrow streets/roads. You each spend 700 or 800pts to buy dreadnoughts only. (throw the FOC out the window for this scenario) You should end up with around 5 or 6 dreadnoughts each depending on what you field.
Play the game as you normal would play using all the rules as per codex and rulebook with only a few minor changes.
1. Each Dreadnought has a total result of 4wounds or structure points. Once reduced to zero the dreanought becomes a wreck on the battlefield blocking LOS etc as usual.
2. When you score a glancing OR penetrating hit on the enemy it automatically causes 1wounds to that model. (do not roll to see what happens for crew stunned etc just yet)
3. For every wound caused in the shooting phase roll 1xD6. On a roll of a 6 the ashot causes a critical hit and you then roll the dice to see if it causes weapon setroyed stunned etc. If you roll a vehicle destroyed then treat the result as an extra wound instead. (You can imagine that as there are only a few enemies it is harder to be stunned as the crew are aware of enemy numbers so aren't as easy to become disorientated)
As I said above I have play tested this and it was lots of fun with several dreadnought CC battles. It uses all the 40K rules as normal with the minor exceptions included above and can easily be played by Space Marine, Chaos Marines and Orks armies.
Give it a try and let me know what you think. (some of you may have noticed that this has elements of battlefleet gothic in it, which it does and was used to make this scenario longer lasting and enjoyable)