If you run Mac OS X Yosemite, don’t use an emoji in your password
As at least one poor soul found out the hard way, there’s a very good reason that Apple’s latest OS X, El Capitan, doesn’t let you use an emoji in your login password.
Apple doesn’t have the same rule with OS X Yosemite. A user on Stack Exchange’s Ask Different forum explained that he had used an emoji in his password on Yosemite — and then wasn’t able to log in to his account. He originally posted about it back in August, but it’s a PSA worth repeating.