From the look of it joint rotation is your best bet and you will have the most control. For the writting on the wall part, you have a few options. One way is to point constrian the gun tip to a locator then animate the locator to spell out the name.
I am enough of an artist to draw freely upon my imagination, knowledge is limited, imagination encircles the world. (Albert Einstein)
For something more "automated", you can use a combination of IK chains and constaints to animate the gun. You'll need to be very careful about where you place pivot points and how you setup rotation limits, but it can be done. With this kind of setup, rather than rotating each joint to aim the gun, all you'd need to do is animate a target and the gun will follow.
take a look at the attached zip (scene file and example movie). is very crude but should give you an idea on how to go about doing it. one thing thats worth mentioning is that when aim constraining its quite common for the local rotation axis to need altering (ie if you do an aim constrain and it aims in the wrong direction or somthing). hope this helps, and any questions ask away !