A flashlight would weigh 1 pound and have a science requirement of 10. When the flashlight is turned on, it will be aimed and whatever you are targetting, illuminating that item/NPC. It would also increase your chance to hit against your target.
A portable Force Field Generator would weigh 60 pounds and have a science requirement of 150. The generator takes 30 seconds to set up but can provide you with valuable protection from bullets, the downside is you can't fire from behind the shield either.
I don't know if items will have Durability; but it stands to reason that a higher Science skill would slow the rate of degeneration while using Energy Weapons. A person with a low science skill could still use energy weapons, but might break them during use ( or fry themselves )
By using weight on science, it limits players to a more realistic range of technology, instead of having a limitless spellbook to choose from. If a player wants to change out the technology he's using, he can either run back to where he stores his gear.