I've never had much interest in getting a tattoo, Pokemon-related or not. If I were to get one, I have no clue what I'd get it of. Maybe one of my favorite Pokemon, like Blastoise? Overall, though, I don't think Pokemon tattoos would necessarily age very well (even if I continue to like Pokemon as the years go on, which seems likely at this point, given that it's been 15 years and I've shown no signs of letting up).
For people who want Pokemon tattoos, maybe a design that also looks like something in nature could work well. Something subtle that could more easily be justified to an anti-tattoo employer would be best (i.e., having a cartoonish character on your arm might not signify maturity and professionalism, depending on your career field).