|Not my model. Griffin Painting - Cool Mini or Not|
The most obvious of course is using a sniper rifle. The Precision Shots on 6s mean we can use units with sniper rifles to pick off particular models from an enemy unit. This is great for taking out that melta gunner or power sword guy. Of course characters can still be saved using a Look Out Sir! roll but your average special weapons guy will die, especially if we manage to rend with the sniper rifle. There are lots of different units that can take sniper rifles of some sort e.g. hexrifles for DE but teams of them are going to be the most effective. I'm considering a different role for my wolf scouts as for 18pts each you get a BS4 sniper rifle. Granted they can't have camo cloaks so you trade the improved BS for less survivability.
On the subject of wolf scouts, when I first read the line saying units arriving from reserve can't assault my first thoughts were webways and wolf scouts. However, on reflection wolf scouts can still be effective. They're still just as good at coming on from the back of the field and putting shots into rear armour (and thanks to hull points they should always kill a vehicle). The other thing they can do is the second kind of sniping I want to talk about, outflanking. One of the most talked about changes for 6th edition is the wound allocation mechanic. Essentially it means that people keep their special models behind a wall of ordinary guys as a meatshield. However, by shooting at that unit from the side or rear we can do more significant damage to it. This is where wolf scouts come in. You could give them all boltguns and maybe a plasma gun to attack a unit from the back and pick of the juicy targets.
The other way of doing this is with outrageously fast units such as dark eldar raiders. Fill them up with kabalites and blast them at full pelt down the flanks. Turn two move round the back of an enemy unit and unleash hell. Your opponent will either have to risk changing formation and exposing the unit to the rest of your army or try to deal with the outflankers and leave the rest of your force to advance. It's becoming more important than ever to avoid just coming at your opponent in a straight line. This is really going to upset any tanking techniques (as I discussed here).
There are lots of Barrage weapons in the game but it's rare that they get used. When was the last time you saw a whirlwind for example? The advantage of a barrage weapon in 6th edition is that wound allocation is done from the centre and you get to pick which model to centre the template on. Granted the thing might scatter but there's a 1 in 3 chance you'll hit the target and likely kill the model you picked out. I think we'll probably see barrage weapons thrown in for just this reason. Imperial guard mortars are dirt cheap and could be picking off meltagun wielding models to protect their leman russ tanks.
As I mentioned above in the sniper rifles bit, precision shots are great for taking down particular models from a unit. My problem is remembering to roll the character's dice separately and actually noticing the 6s rather than just worrying about hits and misses. This is one of those things that will become second nature over time but at the moment this will separate good players from great players.
As with any new mechanic the question is how to take advantage of them in your army. Well personally I think the character with a plasma pistol might see a return. I think plasma in general got a lot better. It may be expensive but you can glance vehicles nicely (and get +1 if you pen), take out particular models if you get a 6 to hit and deal with those pesky terminators. If the rumours are true about DA getting some resistance to Gets Hot! damage then I think they could really be a force to be reckoned with.
Whilst the units I've discussed here weren't that common in 5th edition I really think in 6th they're worth a second chance. I'm a big fan of force multiplication and sniping is a great way of doing it. That whirlwind might be weak against MEQ but if you drop that template on a guy with a power fist then you might keep your T4 independent character alive in his next assault.
Let's not forget that 5 out of 6 games will now feature objectives so space marine sniper scouts could be of more use than tactical squads thanks to their camo cloaks. I think we all need to go back to our codexes and look at units that we'd previously written off and see what they have to offer us in the new edition.
The important thing is to not only think about how sniping will help you deal with an enemy army but also how you need to design your army to deal with it. Deploying and moving your units could now be the most important part of the game!