Gamers here is the list and guide for Gears of war 3 medals which you will be getting during the multiplayer. Each medal you wil be getting it as you do different types of moves, kills, reloads etc.
Active Reloader- 25 perfect active reloads. (0) 4,9
Active Reloader- 100 perfect active reloads. (1) 28
Active Reloader- 300 perfect active reloads. (2) 2
Assistant- Get 25 assists in Versus multiplayer. (0) 4,16
Assistant- Get 100 assists in Versus multiplayer. (1) 5
Assistant- Get 500 assists in Versus multiplayer. (2) 11,19
Beta Tester- Participated in the Beta. 13
Captor- Kill 5 enemies with a captive. 18
Explosives- Get 10 explosive kills. (0) 9,22
Finisher- Get 10 executions. (0) 16,26
Finisher- Get 30 executions. (1) 1,27
Gnasher- Get 10 Gnasher kills. (0) 14
Gnasher- Get 50 Gnasher kills. (1) 8,9,11,17
Gnasher- Get 100 Gnasher kills. (2) 20
Hammerburst- Get 10 Hammerburst kills. (0) 25
Hard Target- Get 10 Last Man Out ribbons. (0) 17
Headshot- Get 10 headshots. (0) 19,27
Lancer- Get 10 Lancer kills. (0) 4,10,26,27
Lancer- Get 50 Lancer kills. (1) 12,24
Master At Arms- Bronze medal 5 starting weapons. (0) 2
Medic- Revive 10 Squadmates. (0) 1,6,16
The Old Guard- Get the Veteran Gear Achievement in Gears of War 2. No video source, Hooligunn's word is bond
Old Schooler- Curb stomp 25 enemies. (1) 19
Pistols- Get 10 pistol kills. 18
Retro Lancer- Get 10 Retro Lancer kills. (0) 1
Sawed-off- Get 10 Sawed-off kills. (0) 2,15
Shock Trooper- Earn 10 First Blood ribbons. (0) 1,11,12,22,24,27
Special Teams- Get 10 map-based weapon kills. (0) 9,10
Special Teams- Get 50 map-based weapon kills. (2) 22
Spotter- Spotted 25 enemies. (0) 3,5,27