The Colt 1911 is the first gun that can be purchased after visiting the Shop in Dead Trigger. This pistol is initially very strong against zombies, though later on it takes more bullets to down one zombie, versus the multiple zombies it could down before. When fully upgraded, it can take as little as one shot to kill a zombie, and with the maximum clip size, it can easily take down a very small group of walkers.
Although most would consider the Colt 1911 to be the weakest weapon in the game, it isn't. Although it doesn't do as much damage compared to more expensive weapons, it is still useful considering the starting damage, and, for a pistol, it can execute zombies quickly. This weapon is less used later on, considering that there are better weapons available, such as the sub-machine guns, which are cheap and more effective.
The Colt is more of a back up weapon than anything else. When running low on ammo with other guns, it can potentially be life-saving. Although it doesn't do much good without an upgrade or the Damage Booster, it can still be of use when encountering a zombie or two. It is still recommended to save the weapon slot for another weapon other than the Colt; it should be equipped as last resort.