The Paradox Gun is a pretty weird gun. You get it by defeating Taimotorabaru. It works weirdly: When you press the mouse button, the time will freeze and a clock-like portal will open. When you press T, the time will keep running and the portal will disappear. When you press the other mouse button, the same thing will happen, and the time portal will be connected to the other one. Resume: You can open time portals and freeze the time by doing it. 

Remember: Dont let the time frozen so much, becaus if you freeze the time by 30 seconds or more, a time paradox will happen and you dies.