I used to play with pivot, I got really excited when I could import images of the FPSC weapons/media as sprites and use them. That was awesome. However, lack of contstraints, skeletal construction, better pivot control (lock pivot on x axis, free pivot, constrain sprite to pivot, detach pivot, ect) made me lose interest.
Also I had once came up with a list of commands for a scripting engine so you could automated certain time consuming animations that simply took time, such as a bullet hitting a wall, and the muzzle flash/shell ejection process. These are things that will happen MANY times, and you technically could just execute by telling a premade script to start running on a certain frame.
But yeah, I had a LOT of ideas for Pivot. I was planning on making a clone awhile ago... don't know why I didn't... hmm... 2d physics and lighting would be cool...
EDIT: Oh, my 12 year old friend who really wants to get into CGI, 3D Animation, found pivot through a friend and got HEAVILY addicted to it. This kid was homeschooled also, so he had hordes of time for it. OMG, he made medieval battle scenes of 50+ characters fighting with all manner of weapons, it was AMAZING. And these weren't the short 30 second ones, they would go on for at least 5-6 minutes. It was insane.
Mountain Dew, happyness in a bottle.