My best was years ago, like...early to mid 2000's, I went to the pawn shop in town and was looking at the games and then noticed there was some games in a bag behind the counter that hadn't been put out yet, and realized they were CIB SNES games, in top quality condition. It's a small town, I know the owner enough as a regular, I asked if I could look at them, and yeah...Final Fantasy 3, Super Metroid, Mega Man X. I don't know how I got them, but I got them all for like 20 bucks each. I thought about keeping them, but at the time I needed the money more, so I sold them on Ebay for what seemed like a nice price at the time, I don't remember exactly, like it was maybe a 120 bucks each or around there. Wish I kept them, because I remember they were like the most perfect boxes I'd ever seen, they almost seemed new.
Another that was cool, was maybe 6 or 7 years ago, I was browsing thrift shops, and I hit a Salvation Army and they had a stack of Dreamcast games, I never see those in the wild. Was like 7 or 8 at least and all for like a couple bucks a piece. Nothing crazy rare in them, but it was a great deal and a neat find. When to a different Salvation Army the same day, they also had a stack of Dreamcast games and by the end of it, I had like 15 to 20 Dreamcast games all still in their cases and reasonable condition.
Got Castlevania: Symphony of the Night for a buck at a thrift shop that use to put the Playstation games with the CD's, at the CD prices, though they've changed the prices for them these days unfortunately.
And a fun one, even if it isn't worth much, was I was at a Goodwill, thought "Hey, is that Banjo-Kazooie?" and sure enough it was, not the boxed N64 game, but one of those promo VHS tapes for it which was a great, random, find as that's just as cool as finding the actual game to me to have some old school promo material.
Haven't been finding as much great game deals lately these days. Goodwill never gets games in, the Salvation Army's around here mostly shut down and the one left in the area doesn't have much, and the one regular thrift I go to every week has pretty higher prices these days compared to what they use when I could get deals, like the PS1 games, or once I got like Super Mario World and a couple other games for like 5 bucks each.
