The Science Weapons all use Energy Cells to fire, even the two melee weapons. None of the science weapons has slots for any mods, so you can't really alter much about the weapons themselves. Most players don't really consider any of the science weapons to be particularly powerful, so it's not like these are used to beat the game easily, but they are sought after because of the cool effects they have. Their damage can be increased by Perks that increase the effect of Science Weapons.
How to obtain all the science weapons in The Outer WorldsMandibular Rearranger: You get this by going to Scylla, then enter a building in the Abandoned Mining Camp at the far end of the planet. Click here for a more in-depth guide to obtaining the Mandibular Rearranger.
Gloop Gun: You can get the Gloop Gun by hacking a computer in the UDL Lab on Monarch, or by correctly answering the three questions asked by the computer. Click here for a more in-depth guide to obtaining the Gloop Gun.
Shrink Ray: You can loot the Shrink Ray on a table next to Phineas on Phineas' Lab. Click here for a more in-depth guide to obtaining the Shrink Ray.
Prismatic Hammer: Head to Groundbreaker and enter the crew's quarters just west for the Promenade. Jump up on a set of boxes and enter a small air duct / hole in the wall. Follow this and kill the outlaws in the room you get to, then loot the Prismatic Hammer in the small room on the right. Click here for a more in-depth guide to obtaining the Prismatic Hammer.
Mind Control Ray: You can get the Mind Control Ray by finding the Abandoned Lab in Cascadia on Monarch. When you are in the lab, find a terminal/computer, then jump on the small pad right left to it. Now jump to the next pad, and climb up to set of stairs to loot the Mind Control Ray. Click here for a more in-depth guide to obtaining the Mind Control Ray.