Hadn't seen this thread before so I spent the last twenty minutes twirling through all 500+ posts. What a cavalcade of terrific eye candy! Here's a few of my cards that I would deem rare not due to a pop report number but simply because they rarely if ever show up for sale.
1890s John McGraw cabinet. Can't be too many of these.
1908 Rose pc Moonlight Graham. I've read there's only four known.
1911 JKA Matty. Never see these at auction.
1911 T4 Buck Weaver. Only know of one other.