@rambo @missy
There aren't a whole lot of things that I consider myself an expert in for two different reasons - the first being that it feels arrogant to call myself an expert in something at the ripe old age of 23 and the second reason being that I'm more of a jack-of-all trades kinda guy anyway. But I came up with three things after thinking awhile, one of which is lame, one is cool only because I'm an expert, and the latter is genuinely cool (at least to me it is). I will explain.
My favorite TV show of all time is Scrubs. I've watched all nine seasons at least three times over and some of the better seasons on the order of anywhere from 6-10 times. I can pull out a quote or a funny line from the series off the top of my head with lightning speed. (This is the lame one if you haven't gotten that already.) I have a pretty good recollection of the episodes and can usually nail when a certain story line or plot point was in the series.
The second thing that I consider myself an expert in is Super Smash Bros Melee. The thing is, the latest console that me and my family owned was the Nintendo Gamecube. And me and my brother's favorite game to play on the Gamecube is Smash Bros Melee. Which came out in I believe 2000. So our favorite game to play together for the last 15 years is Smash Bros. I think we've calculated that we've both played anywhere from 10,000 to 15,000 hours on that game. It's kinda scary.
And I'm the king of single player fights. My brother spent most of his childhood trying to get on an equal level with me as Fox. He spent years trying to perfect playing Zelda/Sheik in order to beat me as Fox. And to his credit, he's gotten very good at it. On his best days we tend to split matches about 50-50. On his bad days it tends to go more 75-25 my favor. And while there is a huge drop-off for him from his primary fighter, my drop-off is far smaller. He now hangs out with semi-pro gamers and cleans their clocks when he plays 3 vs 1 against them.
The last thing that I could consider myself an expert in is the construction and features of guitars. I've spent a lot of time in Guitar Centers playing all different kinds of guitars, from the very cheap to some really expensive ones. I've studied how different woods affect the tone of the guitar, what kinds of hardware are available and their pros and cons, the different kinds of pickups that can be installed, the ergonomics of the guitar. It's a lot of stuff that most people don't think about when they go to buy, but makes a huge difference in the sound and playability of the guitar. I've also spent a fair amount of time modifying my guitars. I've swapped out pickups, changed a pickguard, replaced a nut, replaced saddles, adjusted tremolo springs, and tested out different sets of strings. I'm a nut for guitars and guitar gear in general and I've really learned a lot about it just by being curious. (This is the one I think is the cool one.)