Each lumbering mega boss in the game can only be attacked in certain parts of their gigantic bodies, and it's up to you to guide the sword, arrows, and hatred of the game's erstwhile protagonist to these glowing weak points.
As a signifier of vulnerability and the ability to be stabbed, these glowing weak points might not seem like the best idea to base a necklace around but - well - here they are...
These swanky geek pendants are currently available on CriticalHitShop's Etsy store for the rather reasonable price of $16.00. While they're not the most recognizable of geek neck ornaments that one could wear (that prize goes to Squall's Griever necklace), they're classy in their own way and have an appropriate air of subtlety about them.
Also, they freaking glow in the dark! How cool is that?
The answer is pretty damn cool, unless you have any friends who are fanatics for Team ICO's underrated stab-'em-up, in which case you might want to think twice about wearing one of these in low lighting conditions.
As you might expect from the Etsy store name, CriticalHitShop has a bunch of other geeky necklaces available like a glowing life bar (available in full, or mostly dead!), glowing mana bar, and glowing Hadouken pendant for the street fighting enthusiast.
While all of these are cool in their own right, it's the obscurity and epicness of the Colossus Sigil Necklace that earned it a spot on the Object of geek desire list.
Man, I need to place this game again...