that would be the core marksman rifle.
which, from what i remember, looks at being near 1k in terms of materials
(Requires Fiery Core (4), Lava Core (2), Arcanite Bar (6), Delicate Arcanite Converter (2), Thorium Tube (2))
in all honesty, noone uses it because theres much better stuff available in MC anyway, and you pretty much have to be going to MC to get it.
regarding general engineering...
i tend to prefer gnomish, but tbh i dont think it matters much. the main things that engineering is good for are the 'ultra-safe' transporters, and the repair bots. and you can get those for either i think.
i have a feeling that gnomish tends to be items you make once, and use for a long time, whilst goblin is things that tend to be expendable.... but dont hold me to that.