Lucky with Earthbound there
I've bought a few items on blind risk, but the two most memorable purchases of mine were
Wild Arms and
Breath of Fire IV.
I just got Wild Arms at a used game sale at the local video store, because I had just gotten a PS1 for Christmas, and I needed a game for it. I didn't know the first thing about what I should have/would have picked. The only two games that caught my eye were Wild Arms and Persona. I thought Persona looked neat with the 3D navigation and it was obviously in better condition than WA which was in an ordinary jewel case and photocopied cover art. However, something drew me to pick Wild Arms. In the end, I grew to love Wild Arms and it's actually my favourite RPG franchise now, and has yet to be topped (barring Valkyrie Profile) =)
Breath of Fire IV surprised me since the last I'd seen of Breath of Fire at the time was Breath of Fire II, which I had been so eager to try for the SNES. Looks like I skipped out on hearing about BoF III so I thought: "Why not?" So BoF IV became my favourite out of the BoF series, and so I got to hear some great music and play a great game. Going back to III, I realized for sure that I liked IV better.
Jam it back in, in the dark.