UUID as an ActiveRecord primary key
I like non-sequential identifiers for resources. Easy to do in Java (with java.util.UUID) and in Python (using the uuid module). This has been a bit of a pain in Rails, until now - check out Ariejan de Vroom's post. I especially like his solution as it plays well with RSpec, although to be picky I would have chosen UUID.random_create rather than UUID.timestamp_create....