PvE: pure dps build, firearms boosting only, crit chance/crit damage/armor destruction/base damage/headshot/damage to elites, in order of importance.
Health/stam and skill/electronics are bottomed out (its a cover shooter, the cover is your armor/health/mits) , carrying stun sticky bomb and airburst incendiary seeker (stuns come in handy more often than I need more damage), and tactical link.
Talents: one is none, precision, wildfire, chain reaction.
Standard wep loadout:
assault rifle: main - optimal range extensions, crit chance/damage, headshot.
smg: secondary - crit chance/damage, headshot
lmg: crowd control - increased mag size, stability, +threat modifiers, rate of fire
sniper: alternate secondary/distance mob pulling - headshot, initial bullet stability, crit chance/damage
shotgun: Cassidy, emergency "get away from me" - one is none, 8 pellet spread per shot with each counting as one bullet, plus natural wep talents make headshots nearly always ammo free, coupled with infrequent use of wep class makes spending money a better choice than phoenix/materials.
sidearm: sawed off main carry (even faster emergency "get away from me"), tac m1911 + ballistic shield for hard mode fun runs.
Gear add-ons: ammo capacity, armor (optional), burn/bleed resist, scavenging, protection from elites, as many mod slots as possible
Gear mods: all +crit chance firearms mods.
Gear talents: backpack - relentless, chest - reckless, mask - rejuvenated, gloves - savage or reckless, knee - prosperous or perceptive, holster - steadfast or recovered
PvP: always changing to counter current predominate player setup. Mid to high health and mits/armor always a must.
current favorite: high electronics build with stat boosted BFB sticky bomb mod for one-shotting smg rambo groups, doubles as a solid heal class for group support (first aid with booster shot or support station ammo cache have been the handiest for me). Survivor Link or Recovery Link depending on group level/skill.