This a compact cannon design that can fire TNT, arrows, items and mobs. All entities allowed! :D

If you're wondering; the slime blocks are coming next update. You can get them now by using the snapshot version of Minecraft!

I've made a second channel uploading funny live-stream gaming moments! Check it out: https://www.youtube.com/user/ChannelGameMoments

If you're unable to click the chest at the end of the video, click here: http://www.youtube.com/watch?v=4SzFZgbiXcM

Facebook: https://www.facebook.com/youtubemagmamusen

I first saw the basic idea and design by Sethbling. I tweaked it a little and made it fully automatical. Thought I'd share! :)