A tattoo is subjective. Unless you know the story behind what it stands for and why it is what it is, what is a great tattoo to its owner can be an ugly blight to a casual observer. But what makes a good tattoo? Tattoo artists point out that badly drawn or crudely coloured artwork is unforgivable, whereas balance, shape, placement and the emotional connection of the wearer are integral to making a tattoo great. As Professional body piercer Dave Hurban of New Jersey US, inserted four metal studs in the skin of his wrist so that his iPod could sit magnetically attached as part of the latest tattoo on his left arm, we take a look at some of the 15 best and worst tattoos around.