Some recent finds:
BF3 Xbox 360 Premium edition with case, opened, but code was unused, so I got premium(maybe they didn't know how to put in the code) for 5 bucks - today
Gameboy Advance no battery cover (solid blue) for 50 cents - today
Gameboy advance bag with 2 gameboy advance systems (one clear blue, one clear pink), pokemon silver, pokemon crystal, pokemon red, super mario bros for gameboy, kirby dreamland for gameboy, wario land, 102 dalmations, the little light attachment for the advance, a trading cord - all for just 10 bucks (a counter offer to their original 25).
(dad also found and bought me two original gameboys, one green, one grey, for about 5 bucks when I was sick and couldn't go)
Working Nintendo DS with cracked hinge (still playable, just didn't stay up by itself, but I got used to holding it), did have to buy a charger though, but only paid 5 bucks for one online - the system itself only cost 4 bucks, it also came with a nerf case protector but it was a bit broken and kind of useless to me as I'm not a 3 year old. Got it about 12 months ago.
A backup nintendo 64 (already bought one from a garage sale a long time ago for another 5 bucks) with red expansion pack, all the cords, and donkey kong 64 - 5 bucks
Pokemon Soul Silver - 4 bucks, yeah 4 BUCKS

. Had this one for like a year or two before I even had a system I could play it on, until I got that DS up above I was talking about 12 months ago. Best 13 bucks I've ever spent (system4/charger5/game4), it got me back into pokemon games and I put like 230 hours into just that one game.
Action replay for ds - 4 bucks
A playstation move wand for 25 cents.
A working, fully functional xbox 360 controller (no battery cover, but already had like 5 of them from when I bought replacements for my 360 gears special controller, got the battery covers for like 3 bucks on ebay) - one dollar.
Bad Company 2 Ultimate with case (dlc used though, didn't matter cus I already had it from when I bought bc2 and then sold it, got it back at the garage sale) for 4 bucks.
2 broken (but potentially fixable) PS3 phats to practice on (I have a 60gb in my closet about to die from overheating, need practice with disassembly and reassembly and applying thermal paste), plus a tube of arctic silver 5 (plenty of it in the tube), 2 tubes of thermal compound remover, a really good screwdriver, and a ton of good screwdriver bits (like the heads you replace on it) with a gamebit piece as well, so Now I can open up n64 cartridges to clean them. And a physical copy of crysis warhead. Got that all in a box for 8 bucks.
Gran Turismo 5 disc, 5 bucks (kinda regret that one, dlc was NOT on the disc)
Also these aren't garage sale deals, but deals at a tiny little shop no bigger than an average bedroom (not even a master bedroom) called mcmullens this and that.. Got 2 copies of majoras mask for n64, both holographic, kept one, sold the other for 23 bucks on ebay(only paid 5 bucks for each of them), ocarina of time for 5 bucks (though that took a bit of cleaning to make it work, and the sticker is really worn out to the point where you can barely tell what it is, the two majoras masks were in perfect condition though.
I stupidly passed on pokemon black for 6 bucks (passed on it because I didn't know the rarity of ds pokemon games, and because it was bundled with another one, I should have asked if I could have bought it separately, but even if I couldn't, it still would have been worth it).
I'm sure theres more I can't think of at the moment, but those are just some of the things I've found within the past 1 and a half to 2 years of garage sailing, only on saturdays (me and my dad hang out this way). Garage sales are pretty awesome.