I'll second Chrono Cross. If I had to repopulate my PS1 library it would be the first game I tracked down. But going for unmentioned lesser known greats...
Try to find 'Kagero: Tecmo's Deception 2." Story and translation are weak, controls are pretty bad... but it may me the most fun you can have with a ps1. It's a 3rd person trap setting and torture based combat game. Think Marquis de Sade via Wile E. Coyote's ACME catalouge. And the sequel "Deception 3: Dark Delusion" is good as well. Just don't get "Tecmo's Deception" the first game. Totally unplayable.
Try to find 'Kagero: Tecmo's Deception 2." Story and translation are weak, controls are pretty bad... but it may me the most fun you can have with a ps1. It's a 3rd person trap setting and torture based combat game. Think Marquis de Sade via Wile E. Coyote's ACME catalouge. And the sequel "Deception 3: Dark Delusion" is good as well. Just don't get "Tecmo's Deception" the first game. Totally unplayable.