I'm going over the DP database again and only two titles stand out as "rare", and of those, only one is really tricky (not necessarily hard) to find.
1. Keio Flying Squadron
2. Snatcher (more desired than rare)
Are there others you've had problems with? I only need about a dozen more to complete my collection but I don't see any tough ones in there, unless one of the sport titles turns out to be a problem. How about...
3. The Space Adventure?
I never saw this one in stores and it doesn't turn up very often on eBay - at least it wasn't when I was tracking one down.
Thoughts on others?