TweetShot 6.3 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. The actual developer of this software for Mac is Takuto Nakamura. The application is included in Communication Tools.
From the developer:
TweetShot makes it possible to tweet at high speed. You can set your favorite keyboard shortcut and start up in a moment. You can tweet with a total of 4 PNG or JPEG files attached. Yet, you can tweet with just one GIF animation. The app supports launching at login if the option is enabled from Preferences.
You may want to check out more Mac applications, such as MySpaceIM, ISL Pronto or Instant Messaging, which might be related to TweetShot.