The names of pretty much all army ranks are gender neutral. Do a stolen valor and give yourself a rank for a title.

Reverend (Rev.) is also a pretty good title, though you'd have to either associate with or found your own church. Then again, at that point, you've got a church. You can call yourself whatever you want.

Addendum: I appreciate that Dr is gender neutral, I cannot in good conscience recommend that people go around claiming to be a doctor.