Forge Guard
Rune Guard
House Guard
Mjollnirs
Striborgs
Inner Foundry Guard
Magma Lords
Firebreath Centurions
Kilnguard
Emberguard
Disciples of the Ore
Furnaceguard (did I see this one already?)
Added bonus: name one of the weapons "Energy Bellows"
Leadheads
Ironsides
Fire Lords
Hammers
Sledge Hammers
Panzers
Ironclads
Stone Breakers
Richters
Iron Reapers
Heavy Hitters
Shotters
Big Bores
Iron Bores
Gunsels
Widow Makers
Exos
Iron Mongers
Grenadiers
Metal Storm Weapons Specialist
Iron / Steel Dragoons
Crucibles
Calderas
Assuming heat-based weapons:
-Warmfronts-
(I was going to say "Stormfronts", but I looked it up on Google and realised that would be bad...)
Steel Brothers
Burners
Argent Defenders
Bracers
Pyre Brothers
Charsmiths
Bombardiers
Shellsmiths
Volley Guard
Blaze Runners
Ferro Guard
Shield Breakers
Heavy Guild Guards
Steel Brothers
Black Bombardiers
Backbone Bear Brothers
Gunsmiths of the forge
Splatterpacks
Blockers
Big Damn Heroes
The rivets.