Two comic magazines (on two separate occasions; they caught me the second time), when I was 11 or so. Probably worth about five euros in all.

They also banned me from the shop, and I occasionally wonder whether that's still in force so many years later. Especially since it's changed hands a few times since then (it was a stationer's in a railway station where I used to hang out during the winter while waiting for the bus, browsing the comics).