rankdespair
A tiny pairwise-comparison ranking tool. Two cards side by side, you pick one; over enough rounds an order emerges.
If someone shared a voting link with you
It looks like /{set-name}/vote?rater={your-name}. Open it and start clicking. The rankings page for the same set is at /{set-name}/rankings — you can peek any time.
Keyboard shortcuts on the vote page: a/d or h/l (or arrows) to pick A/B, s or space to skip. b also picks B if that's the muscle memory you reach for.