I've been doing a lot of Java2D stuff at work recently, whilst I was doing it I had an idea for a game based on the mole whacking game at arcades of my youth.
The arcade game pops up moles, you have to hit them with with a club before they go back down. The more you hit, the better your score.
I thought this would would translate well to a desktop time passing game, and provide a good opportunity to sharpen my Java2D skills in the process. The latest development screenshot:
I've got ideas for more features such as a high-score server and different modes of gameplay. Check out where I'm up to at the moment by grabbing the latest development release: https://sourceforge.net/projects/whackattack/