The Hypno-beam is a device created by Jimmy which is able to hypnotize anyone by simply pointing at that person, and pressing a button.
In seasons 1 and 2 it had a swirl on the front. After that, the swirl was removed. But for some reason, in the Season 3 episode, The Trouble with Clones, when Jimmy is in Evil Jimmy's Lab, we can see the Hypno-Beam is exactly as it was in seasons 1 and 2.
It is notably used in the Jimmy Timmy Power Hour by Timmy, where he uses the Hypno-beam to hypnotize and take control of Judy. With Judy under his hypnotic mind control, he eventually makes her think she is Mighty Mom.