Cutting a custom set of Spark Plug wires.

Like the tool that comes in the box?
LOL! Just use a vice.
Otherwise, like the above posts state, that's how it's done best IMO.

EDIT;
The above pictures of my wife's engine bay contain imperfect length wires. But that's just getting real nitty gritty on the matter. Just take your time. Drink your drink, play the tunes, chat away, take your time.