I bought a house a few years back (don't live there now thankfully). The guy moved out and didn't bother to clear the attic out. I couldn't be bothered either and had no need to store anything up there or to even go up there at all in the 3 years I was there.
When I came to move from that house I decided I needed to clear the attic (even though none of it was mine - and because certain paperwork states you have to clear your rubbish out unless the purchaser agrees to take it off your hands).
Anyway, I shifted the old mattress, the odd shoes and broken rocking chair etc. and had cleared everything out apart from a smallish cardboard box which was pushed right to the back of the attic space. I could only reach it by using a broom and a coat hanger taped too it. I reached the box and was shocked and disgusted with the contents. All manner of filth that I don't really care to describe, but the owner of it would have a tough time convincing someone they weren't a peadophile... I thought the police might be interested so handed it in at the local police station along with the name of the previous house owner. I never heard anything back from the police.
By all means, check your attics ladies and gentlemen, but you might not just find the Holy Grail or the original copy of the bible.... you may just find something you wished you never had.
It was a real 'Seven' moment!