There were quite a few interesting Karlssons Klister outdoor executions in Stockholm this week - sadly the best one (possibly) was taken down before I had time to photograph it. In that execution the entire inside of an bus-poster had been removed (no lights!) so you could look straight through it and the text read "in case of emergency, break glass", inside the glass was a single real tube of Karlssons. Having broken a heel or two chasing after a bus I found it to be highly appropriate, and possibly even useful.
Here's one that failed though. When advertising a super glue, the glue must work. The keys on the screen might have been "ctrl" and "z" but as you can see, now there's only Z. They used double-sided tape, same mistake as the Sydsvenskan diary billboard made.
I saw another one as I was dashing to my train, a poster stuck slanted high up on the wall between the "real" poster sites at the central station. Didn't have time to snap a shot, but the placement was funny.