Little Giant. You have proficiency in the Athletics skill, and you count as one size larger when determining your carrying capacity and the weight you can push, drag, or lift.
Titan's Endurance. You can supernaturally draw on the might of your Giant ancestors to shrug off harm. When you take damage, you can use your reaction to roll a d12. Add your Constitution modifier to the number rolled and reduce the damage by that total. You can use this trait a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.
Fire Forged. Your ancestors could bathe in molten steel and you inherit a fragment of this ability. You have resistance to fire damage.
Headstrong. Fire Goliath's are known to act before they think. You add your proficiency bonus to initiative rolls.
Natural Smith. Your people's mastery of metalwork is part honed skill, part intrinsic talent. You gain proficiency with smith's tools.