Are there any tattoo places where you don't have to be under 18?

Assuming you mean "over" 18... No. Not in America, not if it's a legitimate shop, and one in which you won't mind shedding a few drops of blood.

The shop I go to won't tattoo minors under 16 at all and they require that the guardian be present (no written consent shenanigans) and that both the guardian and the minor have photo IDs. In 2010, the state of Minnesota will start to require that it be a state-issued photo ID.