Tusks/Spikes/Antlers

Spikes should be a new drop from elder guardians, with a 85% drop rate. They can be used two ways, one is to upgrade armor in to spiked armor (smithing table), and the other is to make giant arrows (fletching table, bundle of twenty). Spiked armor has the thorns effect, and also a unique one: if a player takes damage from cactus, the cactus immediately breaks, preventing them from further harm being done. Giant arrows are crafted in a fletching table using the normal arrow recipe, but substituting a spike or antler instead of flint. They have a higher arc in their flight path, and deal extra damage.

Tusks are dropped by hoglins, with a five percent drop rate. They can be used for spiked armor, but not giant arrows. 

Antlers would come from a brand new mob: elk. You don't get them as a drop (animal cruelty is bad), instead, you shear an elk. Shearing them makes them drop the antler, and turns them into deer, another new mob (drops venison, but again, animal cruelty=bad). Antlers can be used for giant arrows, but not for spiked armor. Alternatively, you could throw them into a crafting table with three sticks to get "fake antlers," which you can wear as a head item, just to look cool.