Everyone, no matter what part of the hobby they're involved in, has at least one hobby-related something they can't live without. As a tack maker, I have quite a few somethings, so I'm going to share a couple!
Okay, so this one isn't new to most people. In fact, it's pretty obvious and already used a lot by other tack makers. Me? I discovered them exactly three weeks ago. I can be a little slow on the uptake sometimes. They're perfect for holding pieces together while glue dries. I'm sure there are other uses, too, I just haven't found them yet.
Sharp Pointy Objects
Needles, straight pins, and my personal favorite: a random sculpting tool that I bought from a garage sale. It's got a stiff metal rod in a wooden handle that's pretty comfortable. Probably through misuse, the very tip is slightly bent. This is actually hugely helpful, since it makes a slightly larger hole than might otherwise be expected. It's great for punching holes for fake buckles, stitch marking, and removing any excess glue that might seep out. Needles are pretty obvious: good for lacing reins and any other sewing. Tip for lacing reins: turn your needle so that the eye opening is perpendicular to the lace, so that there's less stress on a narrow part of the rein.
I only use one pair of scissors and I've had them so long it's unbelievable. Slightly larger and definitely more pointy than school scissors, they're the perfect size for the leather I work with the most. They don't handle thicker leather very well, but that's okay. I sharpen them periodically with scissor sharpeners and pray that I never lose them, because I haven't seen a pair like this in years.