Danger. Then you can tell people Danger is your middle name.
I actually seriously considered changing my middle name to Danger last year. However, I decided it wasn't worth the trouble for a cliche pickup line due to me being a dual citizen, and a resident in another, so I'd have to change my middle name in 3 different countries.
I don't have one and just pick random letters or names when it doesn't matter. Then I know which ones sold the info to the marketers. "Oh the place I have the X name to is now spamming me with junk mail..."
For more Irish cred, one can of course include an apostrophe as well as the other means mentioned elsewhere in this discussion. Verilog is quite useful in this regard, because of the way that one writes hexadecimal constants.
John 003'hdeadface Smith. Known as "six" to his friends.
No, keep the leading 0x. John 0xdeadface Smith has the added social advantage of also enabling the 0pointer-is-superuser security hole in older versions of systemd, if one can convince people that one never goes by "John". (-: