Equipment Traits

Tool using sapient beings have mastered the more physically adept beasts of their environments by not only mitigating personal risk to themselves through tools, but also negating those beasts' natural mobility advantages through tools as well.

When you cannot run, swim, burrow, or fly as well -- or at all -- as the common beasts surrounding your natural world, how does the society of a sapient species hope to keep up, let alone thrive, in such a competitive environment? Tools, and lots of 'em.

So tools that mess with mobility -- nets, nooses, hooks, and barbs -- are very much part of the sapient tool users' arsenal in competing with their environment. And often these same tools double utility during combat with other sapient tool-using creatures, especially when magical means come in to mimic mobility advantages.

(An overdue equipment gap for several editions, in my opinion. This is the big solution against flight, swim, burrow, and high move Speed. And this solution is older than human written history. Flying spellcasters and magical creatures are toned way down when they cannot escape out of martial range so easily.)

New Equipment Trait

HOOKED & BARBED
Many of the PHB Equipment List weapons can have variants with the Hooked or Barbed trait. They often trade out their damage for lower damage die. But in return they are specialist tools that exploit this trait to deny mobility to such advantaged opponents. It is completely expected for more than a few combatants to have a spare specialist tool in case to counter such mobility advantages.

Hooked - the weapon can make a special melee attack that uses one of the attacker's attacks, which for the most part works like Grapple in the PHB. However, the target of this grapple rolls their check at Disadvantage, even in their attempts to break free. The Grapple does only 1 damage if it hits. It invokes Disadvantage by seeking any easy exposed means to ensnare (fur, clothes, armor) thus not targeting AC.

Common Weapons with Hooked trait: several polearms, like Guisarme and Fauchard, Gaffs, Meat Hooks, Sickles, Sais, etc.

Barbed - like a hooked trait except for ranged weapons. The target rolls with Disadvantage during grapple checks against this weapon. The range weapon can be thrown or a launched missile, but can only limit mobility as long as there is an attached tether (rope, twine, wire, chain, etc.). This trait does not normally affect the range or attack roll. 'Hooked' using the barbed weapon's Grappling attack does only 1 damage when it hits.

Most barbed weapons are sold with a tether equal their Max Range plus 30'. This commonly provided tether also can only hold a max tensile weight roughly equal to the average weight of a medium sized creature. These tether do add up in weight and thus are not carried in abundance on one's person.

Heavier tethers are made and sold, easily up to Gargantuan and larger sized creatures with tensile strength capable to the task of, if not restraining and reeling in, at least maintaining and eventually exhausting the creature so attached. Such tethers often cost much more, and bringing down such larger targets requires a coordinated team. But bring down horses, even elephants, for taming, let alone hunting down whales, is very much within the scope of barbed and tethered weapons success.

Common weapons with the Barbed trait: harpoons, tridents, fishhooks, barbed arrows, tethered darts, etc.

Here is a link to file for review purposes.  There are some internal links in the pfd that are broken.

https://dl.dropboxusercontent.com/u/7962461/Compiled%20Equipment%20by%20Lance%20Hav.pdf

Pathfinder also has their Ultimate Equipment book that may be of some use as well.

Hey now... Thanks!

Just the arrow section alone has some useful variants with rule tidbits to build upon. A massive project, but this makes a nice cross-reference for 5e conversion.