Dave Richeson over at Division by Zero has a post today about ambigrams. Ambigrams, also known as inversions, are words that have some sort of symmetry. In the post he shares some of the ambigrams he’s created.
I am, sadly, not so creative. Fortunately, there are some computer programs that do the work for me! FlipScript (again from Dave’s article) does a nice job, but they’re strict about copyright (you have to buy the images to be able to show them; still, many are worth buying for a special occasion).
Ambigram.Matic has a more public generator. The script isn’t as fancy, but they write that the intent isn’t to be a finished product but just a starting place. Here’s one they came up with:

Not too shabby! Be sure to take Dave’s warning seriously about these sites, though — they can be amazing time sinks.