I'm respeccing my Munitions character and the build I have so far is:

Build by championBuilder 0.3.2

Download this Build here.

: Level 40 Champion

Superstats:
Level 5: Super Dexterity
Level 13: Super Ego

Powers:
Level 1: Gunslinger
Level 1: Two-Gun Mojo -- Rank 2, Rank 3
Level 5: Killer Instinct
Level 5: Jet Boots -- Rank 2, Rank 3
Level 8: Gatling Gun -- Rank 2, Listen To Reason
Level 11: Regeneration -- Rank 2, Rank 3
Level 14: Energy Shield -- Rank 2, Rank 3
Level 17: Shotgun Blast -- Rank 2
Level 20: Sniper Rifle
Level 23: Mini Mines -- Rank 2, Wall Of Fire
Level 26: Orbital Cannon -- Rank 2, Anvil of Dawn

Talents:
Level 1: Quick Trigger
Level 6: Enduring
Level 9: Tireless
Level 12: Impresario
Level 15: Worldly
Level 18: Amazing Stamina
Level 21: Quick Recovery

I took DEX and EGO as superstats for maximum critting, and then stacked REC to get the best out of regeneration and keep my energy up. Two-Gun mojo is my main attack, I took Orbital Cannon because I love using it, I've never used Minimines but I hear it's way too powerful. I'm not really sure I want Sniper Rifle but can't think of anything to replace it - my character looks awful holding the Assault Rifle. I considered taking DEX and REC as superstats and then focusing on EGO instead, but I like the big crits.

Post the entire build up to lvl40. It'll give a better perspective.

You'll want to take Lock & Load and probably Resurgance as it will not only heal you for a quick burst, but also buff your regen rate.

Also, I know the general consensus for Energy Shield is Rank 2 and it's advantage but I'm really not sure why - you should look into that.

ES's advantage gives a bonus to melee, so I'm not going to take that. I don't know what I'll be getting past level 26, so I need advice there as well. The real question I have is whether I should take DEX/EGO or DEX/REC as superstats.

DEX/EGO.

Right now I'm running a Munitions/Ego Blade build with Regen as my passive. I have DEX and EGO as superstats with REC handled through some gear and talents (DEX, EGO, DEX/EGO, DEX/REC, EGO/REC, etc). I rarely have trouble with Rank 2 Regeneration and Rank 1 Resurgence.

Past lvl26 I'd pick up Lock & Load, Sonic Device w/Deafening Dissolution and probably Nanobot Swarm w/Rejuvenating Injectors. You'll have to use Lock & Load strategically, but you'll be critting so much that Killer Instinct will keep you well stocked with END to use your non-Munitions powers. Sonic Device will turn your Shotgun into OMGWTFBBQ Gun O' Fun*. Nanobot Swarm will allow you to heal twice with Resurgence very quickly, as well as use Sonic Device twice along with added a 12 second HoT.

I know that Lead Tempest LOOKS cool, but I've yet to unlock it so I can't vouch for it's usefulness.

* - If you ever want to see something really cool, go to Powerhouse and take SD w/ it's advantage and Breakaway Shot. You look like you just came out of a John Woo movie. :D

Thanks for your input. I'm using my freespec for this and don't want to mess it up.