Relative to my lifelong geekdom I don't have a huge amount of exclusively nerdy accessories but here is my growing collection.
From left to right: Game of Thrones Hand of the King pin and House Stark medallion (Amazon), Batman ring (Ebay), Zombie necklace by Kreepsville 666 (via Ebay), Lego block pendant, Raphael and Darth Vader badge (Thoughbubble Leeds), Robot badge (Designer Marketplace Middlesborough), Nuka cola earring and necklace (handmade by me), FMA Edward Elric pin (Ebay), Domokun necklace, Monopoly house earrings (Designer Marketplace Middlesborough), Dice ring (Handmade by me), SLR Camera necklace (Thailand), Joystick earrings, Batman badges (free from Birmingham comic con), Princess Mononoke badges (handmade present), Xandir from Drawn Together badge (handmade present), Black Jack badge, Charlie the unicorn badge (handmade present), Pacman Removals Badge (Ebay), Dick Tracy 'the kid' badge (childhood), Saturn Ringmaster (childhood), J scrabble tile ring (handmade by me), Doraemon/Robot slides (Thailand), Batman watch (Ebay)
These are two of my favorite badges and I wore the 'I am Batman' badge for a long time on my jacket (hence it's a bit bashed). The best thing about them? They were free! In a bag of goodies at a Birmingham Comic Con they coincided with the death of Batman (obviously) and I had a lot of fun declaring I was Batman for most of my final year of university.
I made these nuka cola pieces of jewellery to go with my vault dweller costume I made one Halloween a few years ago. They were surprisingly easy to make although I'll be damned if I can find the other earring o_o. Maybe I'll share the whole costume someday (the pip boy is more impressive) and exactly how I made these.
I bought both of the above after finishing season 2 of game of thrones. That and the companion book o_o I know, nerd much? The Starks being my favorite family I bought their medallion and it's hefty enough that it feels almost medieval. I have yet to wear the hand of the king pin mostly because I'm almost certain that spike will get snapped off the moment I do.