@ TheBeastlyNinja Here are some screenshots. My older, better design got deleted when I jailbroke my iPhone, so I just made two simpler designs using the wheels. The full auto one has a rotating piston which continuously pushes the rods into the rotating wheels. The 2nd design (which was made earlier) involves a push rod attached via springs onto the frame. The elasticity is set to max and to fire, you simply pull the push rod back, then the springs pull it back forward so it rams the bullet and sends it flying (similar to a real gun except it doesn't have a primer/gun power, obviously). Then there is Steve who is a little test crash dummy that I made. I've had fun attaching balloons to him and putting him in a car and crashing him into a wall (what he was designed for). I might make a V2 Steve with elbow/knee joints, if I have enough time.
I have know idea what I meant yesterday when I posted a bunch of smileys. I probably meant to reply to the previous post. Anyway my favorite physics game is Fantastic Contraption by a LONG shot. With tons of difficult levels, online user content, and a level creator. Nobody can ever finish the game. I am not even remotely close to finishing the offline puzzles (been trying to stay away from online solutions). That leads me to another feature, online solutions. Upload your solutions and check out other users'. Another game that really got me interested is iBlast Moki. It looks very Fantastic Contraptionesque but with different enough gameplay. I had a lot of fun with Tiki Towers as well (a dollar well spent).
iBlast Moki will blow all physics game out of the water. That being said, I'm picking up Toy Box right now.