Favorite:

Combat Rifle (mine does +50% Super Mutant Damage, named it the Mutantilator )

Deliverer

Sniper Rifle

Focus Laser Rifle

Good:

Assault Rifle (looks good while wearing power armor)

Gauss Rifle (this is a monster)

Combat Shotgun (for ghoul stomping)

Plasma Sniper (only decent looking Plasma variant)

.44 Revolver (love the look)

10mm Pistol (silenced this thing looks sixy)

Minigun (three barrel version, no bayonet looks sleek)

Dislikes:

Submachine Gun (wastes my combat rifle ammo, preferred the grease gun 10mm SMG)

Most Plasma variants (looks like someone modded the crap out of a microwave)

Junk Jet (Should be called the Jank Jet)

If I think of more that I've tried then I'll edit.