I have a very big hobby in electronics, which involves making circuits that may contain thousands of parts in them and take hundreds of hours/days to build (yes, I keep track of how many hours it takes, as well as days, number of parts, IC chips, as well as parts per day, etc). To get an idea of how big, I have made 71 circuits (excluding some simple circuits I made) which collectively contain over 100,000 parts (many of which I get from electronics put out by the curb, although I also spend ~$500 a year on parts), going back to 1995 when I was 10 at the time. All of the stuff I have made is also self-designed; some of the sections may be based on existing circuits that I saw in books or the Internet but for the most part I made them using just my knowledge about electronics. One example is a circuit, which I call a matrix generator since it produces a rectangular/square matrix of cells/pixels on the screen (a CRT, with custom-built driving circuitry, or LED dot-matrix display, the latter meaning up to 100 or more 8x8 displays put together) which works like a computer’s video card, a form of dual-port memory which uses a couple memory chips such that one is being read to produce a video signal and the other is written to by the CPU, then swapped around during vertical refresh (a similar circuit is used in the monitor to generate the actual video signal, except the address lines connect to a binary counter so a serial clock/data line can be used).
I have a wedgie* right now*.
Ooh, I’ve got one. Not for me, but my husband.
My husband included a veiled reference to the X-Men in the acknowledgements section of his dissertation.
On the other hand, I got it right away…
Pretty much everything.
The nerdiest thing about me is that I don’t believe I’ve dated any guy who WASN’T a geek/nerd. But I suspect I’m more of a groupie than a geek myself. (I am nerdy enough to know there IS a difference twixt the new, not geeky enough to remember what it is. 
)
I can’t quote for shit, so nerd-quote cred is out.
I’ve done tech support for computers and printers but only built one of my computers myself in the last 18 years of computer ownership, since I’m aways around guys who think they can do it better. (They may be right, but I have done it myself and would do it again so neener)
I named all 3 of our pets after Dresden Files characters.
I’d wear MrTao’s Jayne hat unironically if we didn’t live in the middle of the Tattoine desert. (Seriously, the Sarlaac pit location is about 30 miles from here!)
When the word ‘captain’ comes up, I think of Picard, Kirk, Reynolds and Harkness, not ‘the guy who’s flying our plane’.
I’ve taken off work on the release dates of every online mmo I’ve ever played, which still doesn’t amount that many; EQ was my first, not very geek-worthy.
I’ve somehow ended up with CEs of the last few games I’ve played, mostly because people think I’m geekier than I really am. Seriously, what am I going to do with this Malgus statue?
I have a Figureprints statue of one of my WoW characters…again, Mr.Tao thinks I’m geekier than I am. (Now, one of my DAoC Friar…THAT I’d love!!)
But I don’t min-max for anything, solo unless I’m grouping with friends, and generally treat most mmos like a sandbox. I explore until I’m bored and then move on, unless there are players worth killing ingame; THAT is fun.
When cleaning out the room of MrTao’s sons, who are moving out of state, I refused to throw away the Black Knight <with detachable legs and arms!>, the Darth Vader cookie jar, or the Star Wars comic books. They are now mine!
I am, at best, a borderline nerd. 
The website I maintain devoted to my ham radio activities.
Tapu; How you doin’?
Big train fan. I photograph them, talk about them, and build models.
But NO, I do not have a striped engineer’s cap. That would be silly.
I have a Hylian shield tattoo.
I convinced my coworkers to go as hex colour codes for Halloween.
I’m a walking internet meme encyclopedia.
I used to skip school sports days to stay at home and play video games: pretty much the definition of a gaming nerd.
There was this one smutty fanfic site that required mailed in age verification. Well, there was a script error on one of their pages, so I saved the file, opened it up in a text editor, noticed they referenced a flat file text database for the menu, so I downloaded that file and voila…they didn’t protect the actual story files, just the file that generated the menu. And thus I had my naughty fanfic.
I just asked my wife and here is what she said:
I installed a Merlin Legend PBX in my house just so I could use rotary phones on a VOIP line.
Hey, me too!
Research mathematician with nearly 100 publications. Could anything be nerdier?
I run Science Fiction cons in my free time. I take more vacation for that than I do my actual free time travel.
Even at Cons I do not work, I usually travel to so that I can spend time in the local history museums.
I play trivia games at work.
I spend hours researching miniscule insurance rules and reverse-engineering programs written before 1990 (granted, that’s part of my job)
I’m on the Board of Directors of a non-profit with the term “Geek” in it’s title.
Eli
I play WoW.
My nerdiness is atm mostly confined to culinary endeavors and thus somewhat disguised. Because, who thinks that cherry pie, coconut pudding, or blueberry coffee cake are nerdy? They haven’t seen my date-sorted list of spices currently in stock, nor the date-sorted shelves of grains (pearl barley, sticky rice, basmati rice, flat dried rice noodles, round dried rice noodles, pearl tapioca small, pearl tapioca large, Uncle Ben’s rice, homemade egg barley, 10 lbs jasmine rice), nor the date sorted shelves of legumes (navy beans, adzuki beans, brown lentils, black beans, yellow split peas).
I take it back, I am not nerdy at all! I’m in awe of the nerdiness described in this thread; well done!!!
I have an encyclopedic knowledge of the Godzilla universe.
I can identify every monster by name, description, and roar.
I know who fought whom, who won and who lost, and could surmise pretty well who would win in people who never fought.
I also have a stuffed Godzilla toy I bought on ebay.
The nerdiest? Let’s see…
I once wrote a Turing-bot that got more romantic action than I did.
I once used pickle juice to fix a mistake in a chocolate-chip cookie recipe. And it worked.
Everyone dreams about flying. But while I’m dreaming about flying, I’m also designing experiments to determine how I’m flying.
My Halloween costumes have included the set containing Chronos, the Aurora Borealis, a Newton’s Cradle, the vacuum energy, Great A’Tuin, and the Principal of Superposition.
My degree in Mathematical Computer Science? My compulsive Wikipedia editing habit? The box under my bed that contains a collection of 1:500000 topographic maps of the whole country? Any one of these things.