I had a game recently where the only action card in my hand was Crown. In this scenario I still started in my action phase, which I found counter-intuitive as in this situation you are only ever going to want to play Crown as a treasure. If you have a Crown and no other actions, should your turn skip the action phase and go straight to the buy phase?
See this discussion: http://forum.shuffleit.nl/index.php?topic=1046.0