Which non-energy weapon modifications require the "Science!" perk?

Solution 1:

You wouldn't be able to craft night-vision or recon scopes on any weapons, that will be the majority of what you'll miss out on. The only other non-energy weapon is the Junk Jet which requires 1 point in Science! for some damage upgrades.

Power armor as well, requires Science! for some upgrades. Everything else requiring Science! are energy weapons.

Solution 2:

EDIT: Relevant things that require the Science perk:

• most everything energy-weapon related

• night vision and recon scopes as well as specialised scopes (e.g. Gauss Reflex Scope)

• power armor upgrades

• settlement defense turrets

As per this (incomplete) wiki article right here, you will mostly miss out on mods for Energy weapons and Missile Launchers.

You will also not be able to craft some turrets for settlement defense as well as upgrades for all types of power armors.

Solution 3:

Science! of various ranks provides a variety of weapon mods, for projectile weapons though you'd only be losing out on the recon scopes. That said, recon scopes only require Science! rank 1...

• Recon scopes for most weapons (pistols, rifles, etc)
• Night vision scopes for some weapons (launchers, sniper rifles, etc)
• Can convert a mini nuke into a MRV launcher (requires Science! rank 3)
• All energy weapons, all parts (plasma, laser, gamma ray, etc)
• A damage upgrade for the Junk Jet

Outside of weapons, Science! allows you to upgrade your Power Armor, build laser turrets at your settlements, and more broadly; intelligence helps with some missions (for example the USS Constitution missions) where it opens up some additional options for completing the mission.