One single Chinese character doesn't really make a "word". In Cantonese, the character sounds like "wai". This character is the first character in the Chinese "word" for regret, inheritence, or will (the document).
I saw a comedian who did a joke about those chinese tattoos. He said:
...what if the chinese are screwing with us and telling us improper meanings of these symbols. Some guy is walking down the street with what he thinks is "Power" and "Strength" on each arm, but the truth is, it really says "Peanut Butter' and "Jelly"
(in a bad chinese accent): "You see that guy? He wearing a sandwich."
In Japanese, that particular kanji (or hanzi if you prefer) by itself doesn't mean much of anything. When it's used as part of a compound, it can mean a wide variety of things, but it's not really a frequently used character. Was there any more to the tattoo that might be a clue?
I read an article a few years ago about an asian tatoo artist that actually did this. He said that he was sick and tired of non-asians coming in to get tatoos of symbols that have no meaning to them. I'll see if I can locate the article.
I read that Yao Ming looks at some of the NBA players with tatoos with curiosity because the chinese characters or words often mean something that doesn't make sense. For instance, he said Kenyan Martin sports one that means "hesitant" which he says that's not how Kenyan plays at all.
Oh man, I remember back in August, I saw this custom painted car with a Chinese character on it. I wrote it down, and asked my dad later what it meant. "Urine." Ooh.
"Regret" would be the best start, but without the second character ("hum" in Cantonese, "han" in Mandarin), it doesn't mean much on its own. This would be a strange choice for a tattoo, to be sure.
I'm not necessarily sure it's ethically right to do this to people ever, no matter what the circumstance. Seeing as how one pays you to do the job, you're effectively cheating them out of their money and not owning up to your part by being deceitful, and admittedly childish. However, for the sake of humor, some of the people do seem to be asking for trouble. I mean, for god sake's bring a goddamn Asian friend as a little insurance. Hell, I can't really read Chinese but I'm sure a tattoo artist wouldn't call the bluff of me being there.