Naughty Dog released a full list of the Medal Kickbacks that will be in the multiplayer portion of the game. All of them seem to be really helpful in one way or another whether it is giving you a certain weapon such as an RPG or Bolt-Action Sniper or increasing your damage threshold at the cost of your speed (they call it Juggernaut). Take a look at the full list below as well as a video of the Creepy Crawly kickback that you can get at the start for pre-ordering the game from Gamestop.
Speedy G (Speed Boost)
RPG!!! (Gives an RPG)
Smoke Bomb (Vanish in a puff of smoke)
Militia Man (Gives you half of a clip, increases fire rate and you don’t have to reload)
Cursed Idol (Throw a Idol that releases a cloud of gas that curses anyone who enters it)
Quick Boom (Gernades explode on contact)
Cash’em In (Double your cash earnings)
Sniper (Gives a Bolt Action Sniper Rifle)
Explosives (Receive two grenades)
Disruption (Nearby enemies cannot see player arrows)
Shottie (Gives a Shotgun)
Carpet Bomb (Throw three grenades at once)
Gotcha (Show the location of all enemies)
Cluster Bomb (One grenade explodes into multiple)
Hammer Time (Gives a M-32 Hammer)
Juggernaut (Trade in speed to become nearly invulnerable to bullets and grenades)
Mega Bomb (One massive grenade explosion) and finally Creepy Crawler (Transform into a swarm of spiders).
