DM Whacker is a bulk direct message deleter. It allows the user to delete all Direct Messages (DM's) at once, or simply all the messages the user has received from a particular source.
Note: DM Whacker currently only works with old twitter. I have not had the opportunity to update it yet to work with #newtwitter. If any enterprising dev cares to, the source is here: https://github.com/dacort/dm-whacker
Worked pretty well in Chrome. I don't really have too many relevant DMs and was flooded with all the auto responses from following people so I needed to "whack" away, simple and effective. DM's gone. Maybe now I'll actually start using it again for something worth while ;)
Does what it says it'll do. Mass deletes DMs. I'm not quite sure why people need to delete their DMs (deleting DMs permanently removes the message from both the sender and receiver's In and Sent boxes) but it's nice to have the option if I need to.