As part of spring cleaning, I got out an old box of Sonic the Hedgehog comics I read when I was a kid, thinking I could probably sell 'em for a few bucks online. It turns out, I have a bunch of the rare early comics, including Sonic #0 and #1, as well as multiple complete sets of several mini-series, including the hard-to-find Princess Sally mini-series. I think the reason I have multiple copies is 'cause Archie Comics screwed up my order once and shipped me some extra copies on accident. Some of the comics aren't in great condition, but I think I can probably get half a grand or so for my collection on eBay.
I also went through my old games and realized I have some gems in there, the best one being my copy of Secret of Mana with the original box, manual, poster, and strategy guide. Hopefully I can get $100 or so for it. I also have Chrono Trigger and Final Fantasy VII in their original boxes, as well as other classic games with their boxes and manuals, so I should be able to get a nice amount for them as well.
Next up: my baseball card collection...
Like, there's no health meter or points, because everything's just cool. You don't have to worry about it. And when you come to a boss at the end of a level, you just make friends with them, and then you all party together.