Open U / Double Barrel Crimp Tool
This is a great tool if you are using real automotive style, waterproof, or weatherproof connectors. This will crimp three sizes of open double barrel type crimp terminals, and two sizes of wire seals. Works great with the Waterproof Circuit Breaker Kit, or the Waterproof Relay Kit. But really this is just a good tool to have in your collection.
This is an economy solution to terminal crimping, it is a well-made tool and performs well. It is not as nice as the "official" crimp tools, but it also doesn't cost $400, and it will get the job done. This tool also has a parallel jaw motion which helps keep the terminal in the correct orientation when crimping.