I fell off my motorcucle once, mercifully at low speed, and developed a bruise on my hip that strongly resembled the stars and stripes.
Today’s invention is a temporary alternative to the tattoo.
A small template in the desired shape would be snapped against the skin, probably using a spring mechanism something like a mousetrap. This would create a bruise and with no more pain than the conventional process induces.
It should also be possible to vary the local colour in such a bruise by applying a sequence of differently sprung templates to different parts of the body area involved.
Although this would not give the high definition of a conventional tattoo, this approach has the advantage that, when the love of your life changes, you need not be burdened by his/her initials forever.