Spacer by Sheila B Devotion. As a teenager at the time, I just thought why not, she's gorgous. In Woolies in Portslade, on a Saturday morning, before going to The Goldstone, probably.
Turned out I loved it and still play it loads and loads.
I bought this album simply because the cover was by Roger Dean and I'd read it was becoming quite valuable. Absolutely awful music (or at least I thought so last time I played it 40 years ago). Also features the vocals of 12 year-old Keith "Cheggers" Chegwin. Ugh.
I picked up the original Robert Williams cover of Appetite For Destruction a couple years ago, despite not being a huge Guns N' Roses fan. Well worth it.
Wild Willy Barrett & Two Names' "Organic Bondage" was another album I bought for the cover. Totally unique, each one was personally made out of wood by Wild Willy himself I believe.