I wandered away for a while and when I came back Talmage was calling it a Transformer gun. It turns out it does this:
This would be Megatron. For only 50 cents it was a pretty good deal, as these are selling online for about $100. I'm pretty sure it's pre-2007-Transformers-Movie as Megatron was originally a gun in the cartoon, but I'm not sure when it was made. The kid must have only played with it for a week, though. It's in pretty good condition. Lois thinks it's about 1984, but we can't find anything difinitive online.