This is all the correct answers in one spot:
There are several Synergies that do not require mods. You simply have to have two weapons with the same synergy name equipped (1 main and 1 secondary) for the effect to work. These are: Hard-Boiled, Machinist, Nano-Executioner, Nano-Mastery, Outlaw, Sawbones, Survivalist, Veteran and Wrecker.
The others you have to earn/buy, then equip MODS to the weapon. As you equip more MODS(with the same synergy name), you will activate more perks. These are: Assassin, Brutal, Cannoneer, EGO Precision, Prepared, Quartermaster, Rolling Thunder, Run-n-Gun, Scavenger and Stalker.
Step by step video: http://www.youtube.com/watch?v=OXDZwu07aME
List:
Note: If the Mods can be purchased, I will add the vendor and location to the list. Otherwise assume the Mods come from Synergy Mod Cache sold at any Lockbox Vendor
Synergy: Assassin CONFIRMED
[1]: +2% Crit Mult
[2]: +4% Crit Mult
[3]: +5% DMG on next shot after critical kill (Expires after 10 sec)
[4]: +10% DMG on next shot after critical kill (Expires after 10 sec)
Synergy: Brutal CONFIRMED
[1] +5% Melee DMG
[2] +10% Melee DMG
[3] +5% Reload on Melee Kill
[4] +10% Reload on Melee Kill
Synergy: Cannoneer CONFIRMED
[1] +3% Fire Rate
[2] +6% Fire Rate
[3] +10% nano-effect chance for 2 sec after full reload
[4] +20% nano-effect chance for 2 sec after full reload
Synergy: EGO Precision CONFIRMED
VBI Mod Cache / Shondu’s Consulate (fast travel)[1] +10% Accuracy
[2] +20% Accuracy
[3] +3% active EGO ability duration on critical kill
[4] +6% active EGO ability duration on critical kill
Synergy: Hard-Boiled CONFIRMED
[2] +2% refresh self-revive on a kill
Synergy: Machinist CONFIRMED
[2] Take 5% less damage while reloading
Synergy: Nano-Executioner CONFIRMED
[2] +5% nano-effect chance on a kill
Synergy: Nano-Mastery CONFIRMED
[2] +5% nano-effect chance on a critical hit
Synergy: Outlaw CONFIRMED
[2] +5% damage from last shot in clip
Synergy: Prepared CONFIRMED
Top-Notch Toolworks Mod Cache / Top-Notch Toolworks (fast travel)[1] 1% ammo regen/10 sec
[2] 2% ammo regen/10 sec
[3] +5% DMG on next shot after melee kill (expires after 10 sec)
[4] +10% DMG on next shot after melee kill (expires after 10 sec)
Synergy: Quartermaster CONFIRMED
[1] +5% Reload
[2] +10% Reload
[3] +50% Reload on self-revive
[4] +100% Reload on self-revive
Synergy: Rolling Thunder CONFIRMED
[1] +5% Mag
[2] +10% Mag
[3] +10% Hip Accuracy
[4] +20% Hip Accuracy
Synergy: Run-n-Gun CONFIRMED
[1] +5% Movement Accuracy
[2] +10% Movement Accuracy
[3] +10% Accuracy and -10% Recoil at low health
[4] +20% Accuracy and -20% Recoil at low health
Synergy: Sawbones CONFIRMED
[2] Fully reload weapons after reviving another player
Synergy: Scavenger CONFIRMED
Soleptor Enterprises Mod Cache / The Crater (fast travel)[1] +1% item drop chanceS
[2] +2% item drop chance
[3] +10% nano-effect chance against out-of-combat targets
[4] +20% nano-effect chance against out-of-combat targets
Synergy: Stalker CONFIRMED
[1] +5% Range
[2] +10% Range
[3] +5% EGO ability refresh on critical kill
[4] +10% EGO ability refresh on critical kill
Synergy: Survivalist CONFIRMED
[2] +2% damage to targets with full health and shields
Synergy: Veteran CONFIRMED
[2] +10% rate-of-fire after a full reload
Synergy: Wrecker CONFIRMED
[2] +10% DMG to vehicles
*Only Brutal and Run and Gun are in the Keycode Cache
*Each Faction uses Rep to get their respective mods (Precision [VBI], Scavenger [Soleptor], Prepared [Top-Notch])
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