A German artist named Matthias Megyeri has started a company called Sweet Dreams Security, which makes security items like padlocks, alarms, and razorwire that look cute and happy.
Examples of Mr Megyeri’s art include padlocks designed to look like teddy bears, heart-shaped chains, and glass fir trees embedded in concrete, designed to replace broken bottle shards, which are now illegal.
While they look delicate, the top of the fir tress is very sharp, to deter people from climbing the wall.
Link (Thanks, Carl!)