I was looking for a Christmas present for my Dad in the folk section of HMV today when this birghtly illustrated cover caught my eye - http://www.brightyoungfolk.com/images/records-large/adventures-of-captain-ward-demon-barbers.jpg
So based on only that, the fact I liked the name "The Demon Barbers" and the belief that having 3 people credited as clog dancers could only be a good thing. And having listened to it when I got home I was pleased to find out that not only does it have more excellent art inside but it's a rather enjoyable, lively folk record.
However this style of buying has gone wrong for me in the past. A prime example being an album called Adventures in Fuzzy Felt land by the Kazoo Funk Orchestra. It had lovely art which reminded me of playing with fuzzy felt as a child (http://ecx.images-amazon.com/images/I/51viWeN2YOL._SL500_AA280_.jpg). Alas the album itself was complete pish. Which I suppose I should have realised when the opening gambit was a track called "Shat Upon Your Train."
Anyway, what are the best and worst purchases you've made when judging an album by its cover and/or name?