Ice gun

The Ice gun is a fourth pistol to unlock. It is a custom single-shot weapon that fires very slow ice trails. When hit by one, the opponent freezes. This effect also forces his guns away. However if he spams to bring a weapon it can fire 1-2 bullets. Practically it does no damage to players since by the time they are no longer frozen they heal to full. Adding Fire ammo to the Ice gun will make it deadly causing 50 damage. Ice ammo makes nothing better - do not use it on this sidearm.

Pros

 * Instantly freezes players.
 * Makes the opponent mostly impossible to use his guns.
 * Can be deadly (with Fire Ammo).
 * Good accuracy.

Cons

 * Very slow trails.
 * Trails light all around them.
 * Single-shot.
 * Small ammo storage.
 * Deals almost no damage without Fire Ammo.
 * High cost.
 * You need to go to the armory to get it.

With Ice gun
Try get to the target close enough to make trails effective as they are very slow. Use fire ammo. Once trail hit the opponent, use most OP weapons. Try hitting him again immediately after the enemy unfreezes. Very effective against SCPs.

Against Ice gun
Maintain distance as its trails are slow to have a good chance of dodging from them. Once the Ice gun was used, fight as normally. This gun's trails also light all around them, so you will be aware. If you were hit by it anyway, spam the weapons as this can fire 1-2 bullets from them. If you are an SCP, run from the Ice gun's users as fast as possible.

Trivia

 * Ironically enough, ice gun's trails light all around them as if they were fire ones.
 * Looks like the devs didn't want to make a new light effect so they added it from the flamethrower.
 * One more detail from a flamethrower is a second barrel that is below the main one. It is used to put on fire a special gas going out of the main barrel.
 * Here it may ice the "special gas".
 * The hand glitches out one more time.
 * Ice gun also has an empty spot above the trigger.