I've been meaning to get a tattoo for several years now, and so far I haven't been able to come up with something that is worthy of permanent inking on my body. Not to say I haven't had some great ideas, I just always end up broke by the time I intend to do it, then realize it may be a bad idea.
I came up with an idea to tattoo myself every 5 years. Nothing gigantic, but something that shows where my mindset was at that current time. Something I was interested in, or something I believed in at that time and place. I figure this way, I can never really hate a tattoo, because I'll always be aware of it being something I cherished sometime in the past.
Maybe for my 20th birthday.