Mine are far from being insanely good deals, but anyways...
In January I found a CIB "Rockman X4 - Special Limited Pack" for the Saturn for less than ¥2,000. It had some ugly scratches, but worked just fine and, since it usually goes for around ¥12,000, I think it was a pretty good deal.
Also, I finally got "Herc's Adventures" for the PS1, a game that I'd never played before and really wanted for a long time, for ¥950.
And apart from that, I got something that I never knew existed: "Ace Combat 3 DIRECT AUDIO with AppenDisc" bundled with a "Playstation - the Best" copy of "Ace Combat 3" for ¥250. It's a very interesting 2-discs pack containing the complete soundtrack, a movie player with all the game's cutscenes and a save file that you can transfer to the memory card and unlock all the planes. I love this game, so it was really neat!