Why, it's a leash for a pet rock. These were all the rage back in the 70's.

(I survived the russian meteor, ladies XS)

Oh heavens, the ads in the corner keep giving me ideas! It may be a Thor water bottle or mug! That would be highly exciting. Ah, forgot to read, it says one item per guess? That's no fun!

Ladies' Grey Roflcopter pilot shirt in as small as it comes!

Alternatively, it may contain Thor comics, or a copy of the new Thor video game. An art book is also likely :)

Ladies' Grey Roflcopter pilot shirt in as small as it comes! Forgot to mention size in my previous comment.

I bet the box contains Thor themed merchandise, most notably a small Thor poster as well as a shirt.

Ladies' Grey Roflcopter pilot shirt, if you please!