Gun Master is a type of free for all gametype, but with a team. Even though you're in teams, only one person can win. You start out with a simple handgun (Mp443 I believe) and for each and every gun you have to obtain a few kills, 2.
This is a lot like Gun Game in Blops and CS, there are 17 different weapons to aquire before you win. The final "gun" is the knife and here you only need one.
Full list of guns, sorted in NAME, TYPE OF GUN and NUMBER OF KILLS
1. MP443 - Single fire pistol - 2
2. 93R - 3-burst fire pistol - 2
3. .44 Magnum - Single fire pistol - 2
4. PP19 - Submachine gun - 2
5. P90 - Submachine gun - 2
6. SPAS-12 - Pump-action shotgun - 2
7. MK3A1 - Automatic shotgun - 2
8. ACW-R - Carbine - 2
9. MTAR-21 - Carbine - 2
10. AUG A3 - Assault rifle - 2
11. SCAR-L - Assault rifle - 2
12. LSAT - LMG - 2
13. L86A2 - LMG - 2
14. M417 - Semi-automatic sniper rifle - 2
15. JNG-90 - Bolt-action sniper - 2
16. M320 LVG - Grenade launcher(Does not blow up on direct impact) - 1
17.Knife - self-explanatory - 1
The trick here is to be quick with your pistol kills or else you'll be facing machine guns and shotguns. This will take a few tries, but eventually you will get lucky and win the game!
All of the CQ weapons in gun master can help you towards the 10 kills with each weapon achievement.
In-game, at the bottom of your screen, you can see a progress bar. This will help you to see where other players are and on what kind of gun.
Enjoy the video below by IPwnstar4hire, a gameplay of him winning gun master on Ziba Tower..
To all you that vote negative, please state why in the comments, so I can improve the solution..