A friend ordered a trike in a box a few months ago; the kind that looks like a girl's bike with two rear wheels. I told him I'd put it together for him if he would bring it over.
The bike came with a folding multi-tool. It wasn't mentioned in the instructions. I used my own tools for most of the assembly, then wound up using the multi-tool for most of the fine adjustments. I had no idea such a thing even existed until then. It wasn't a particularly comfortable tool to use, but it sure was convenient, and I plan to order a couple of my own, one for each bike.