Making a sniper

[Quickleaf]

I'm trying to create a good sniper for a D&D game. I'm thinking a 6th level crossbowman, but I'm not sure what kind of feats to give him besides Stealth and Weapon Focus (crossbow). How do I use the cover/concealment rules to determine when a Hide check is unnecessary?

Are there feats which:
- Minimize penalty to Hide check after making a ranged attack from behind cover and seeking to duck out of sight before being seen? Usually this is -20, but can be greatly reduced by being far away.
- Inflict extra damage on a ranged attack at distance, say, from a rogue's sneak attack.
- Allow you to make a ranged coup de grace?

 

[Viashimo]

I built a sniper for a set of NPCs in a Dark Sun campaign I'm working on.
Here's the feat breakdown (human fighter 6)

Point Blank Shot
Precise Shot
Far Shot
Sharpshooting
Concentrate Fire*
Sniper*(reduces hide penalty)
Weapon Focus(longbow)
Weapon Specialization

Why did I use longbow? - more shots, and mighty composite allows for strong archers to deal more damage.

The feats marked with a * denote feats from the Dark Sun 3.5e manual at www.athas.org
sharpshooting may also be from that book, but I can't remember for sure.

The concentrate fire allows for several archers to team together to deal much more dmamge on ready actions, means a couple of them can lay waste to a wizard who is about to start casting or something.

There are other feats, some available only at higher levels, for this build.

 

[Storyteller01]

Pimping a houserule...

We used a variant on the Iaijutsu Focus skill from OA.

Similar mechanics. Target has to be flat footed against your attack [so get great hide checks], one action per round, you lose your Dex based AC while aiming. In return, you roll the skill to determine the extra damage for that shot (10-14 = +1d6, 15-19 = +2d6, etc).