I have all the DLC and such. Looking for an effective build.

Copy-pasted from an old plan for my assassin build. Pretty fun character.

She's a long range assassin... tends to get hurt by my own explosives, though.

Starting SPECIAL: 5/5/6/1/6/8/9. Reached level 50 with 9/6/7/1/7/10/10. 4 points in Strength after 1 implants and all DLC completed. The rest is all implants. Cost quite a fortune, but I did used the FO3 merchant exploit, so caps weren't a real problem. I try to get high Strength in order to use the AMR later, as well as Avenger minigun if I ever put on Heavy Armor whenever I want to mix things up a bit.

Traits: Small Frame (+1 initial Agility) and Trigger Discipline (25% extra accuracy)

Skills: At level 50, I maxed out: Guns, Sneak, Explosives, Repair, Science, Medicine, Lockpicking, Survival, Barter (need for Pack Rat). Speech was at 74.

Perks: (not in order, I picked them depends on what I was facing at the time)

1) Heave-Ho

2) Educated

3) Bloody Mess

4) Dem Expert

5) Dem Expert

6) Dem Expert

7) Shotgun Surgeon

8) The Professional (Glitched perk, said that it gives 25% extra damage for sneak attack with pistols and smgs. But it actually gives an extra 25% damage for EVERY CRITICAL HIT with pistols and smgs. Wonderful)

9) Cowboy

10) Pack Rat (I was playing hardcoe, so I had to carry literally an armory with me)

11) Strong Back (Same reason as Pack Rat)

12) Finesses

13) Hit the Deck (My own Explosives hurt me quite a lot)

14) Silent Running

15) Splash Damage (I actually regretted this perk because my own mines were starting to become a problem mid-late game - with Small Frame I get pretty easily crippled - which forced me to take Hit the Deck to at least relieve some of the damage)

16) Chemist (For extra Turbo and Stealth Boys time)

17) Better Criticals

18) Light Touch

19) And Stay Back! (Great perk. Saved my sorry butt countless of times. Thank you, Dinner Bell!)

20) Grunt

21) Burden to Bear (Same reason as Pack Rat)

22) Certified Tech (Components to make Satchel Charges can be hard to find, but with this perk, every robot I kill has an 80% chance to give me those components. Satchel Charge is like crack...They make me feel safe... One can NEVER have too much Satchel Charges! )

23) Tunnel Runner

24) Travel Light

25) Just Lucky I'm Alive

Play style and load out:

Long range guys kill as far away from the targets as possible. And even if it takes an entire day to kill a target, the sweet pop of a headshot makes it all worthwhile. My assassin also places mines between my sniping point and the targets, just as insurances.

As for the logistic part of the playstyle, I scavenge A LOT in order to get components to make Weapon Repair Kits and Satchel Charges, until I get to OWB then scavenging became trivial. I don't make complicated food or waste ingredients and spaces on them; most of the time I just stick with the 4-meat diet: Gecko, Bighorn, Coyote and Brahmin Steaks; though Bloatfly Slider can be fulfilling as well as easy to make. I also pick up whatever good food I can get my hands on. And the rest of the ingredients I dump into making Fiery Purgative (For rads and poisons) and Turbo. I also have a lot of water handy (HC mode) as well as Atomic Cocktails.

As for early load out for an assassin, I would recommend go and pick up the Ratslayer (use 5.56mm, already silenced), a Cowboy Repeater, a Hunting Rifle, and any reliable shotgun (Your starting Caravan Shotgun is pretty good), but I prefer to use the Lever Action Shotgun until I got my hand on the lovely Dinner Bell. Dynamites and mines on the side but that's up to you whether or not you like to use Explosives).

Later load out would be a silenced Sniper Rifle, La Longue Carabine (Required you to kill an NCR npc, but it's a great weapon), Trail Carbine if you can't get La Longue Carabine, Hunting Rifle, 5.56mm pistol (That Gun can be easily and early acquired in Novac), Lever Action Shotgun, and a Grenade Launcher. The rest is loaded with grenades, dynamites and Satchel Charges... Did I mention you can NEVER have too much Satchel Charges?

My current (level 50) load out is Christine's COS Sniper Rifle (Best long range gun in the game for an assassin, period.), Medicine Stick (as expensive as a Brahmin farm... But I got exploits up my sleeve), Lucky (Require high Lockpicking skill to get), All-American, AMR, and Dinner Bell. As well as lots and lots of Satchel Charges, because... yeah you got the idea.

As for outfit, I rolled with the initial Light Leather Armor and 1st Recon Beret for most the game then switch to Joshua's Graham's Armor, until I got Ulysses's Duster at level 50 after LR (A LONG time, I know). Now I'm switching between U's Duster and Assassin's Suit. Light Armor synchronizes well with Light Touch, Tunnel Runner, and Travel Light.

Note: With both Grunt and Cowboy, Chance's Knife can be quite crazy at close-quarter stealth, so you may or may not want to calibrate your skill points and perks to fit with a Guns/Melee playstyle.

Also, if I wasn't taking Splash Damage and Hit the Deck, I could have gotten Nuclear Chemist and Mad Bomber to make potentially unlimited Nuka Grenades (since HH gave you the recipes to make Nuka Cola). And Nuka Grenades are pretty sweet.