I love these crochet bike dress guards. Originating from the dutch town of Staphorst, they are meant to keep one's dress, coat or skirt from becoming caught in the spokes or worse yet, the chain of one's bicycle. They would also make it way easier to identify one's bicycle amongst hundreds of others locked up within meters of each other at dutch schools, libraries, trains stations or any other public space in the Netherlands where bicycles are practically everywhere (even on the bottom of canals!).
To crochet your own, there are a couple of very cute patterns on Ravelry:
This one is by Dorien from Just-Do's with an open space for your lock.