I think this scenario would apply to you pretty well :)
http://www.rollingstone.com/news/story/21129674/the_battle_f...
But when you're a founder or such, you have to cop to it. You don't want it to look like you're evading responsibility or jerking people's chain.
So it's "CTO and Co-Founder" on my business cards and (when appropriate) on email.
"In 1972, Mobutu renamed himself Mobutu Sese Seko Nkuku Ngbendu Wa Za Banga ("The all-powerful warrior who, because of his endurance and inflexible will to win, goes from conquest to conquest, leaving fire in his wake."), Mobutu Sese Seko for short."
No, but seriously, I use "Principal." It conveys my central role in the company from a financial perspective without having the dangers of sounding pompous, pretentious or immodest to the ears of people who think "President" or "CEO" is a bit lofty for a 1-3 man show.
The signature of a principal is often required in serious contracts. In other words, the defining attribute of a principal is his or her ability to represent the firm in a legally binding way with no limitations.
Do what you say, say what you do.
For example when I am prospecting work for my day job I always use "VP <company>" or "Senior Analyst"
On the other hand for my own company I usually choose something light heartened related to the rest of the mail: "the man" or "the tech guy" etc. it goes down quite well.
I usually don't put any titles in the actual email itself. In the signature, I sometimes go with Co-founder, other times, just put the company name.
I earned those letters dammit!
Still, at least it's a respectable degree. I once had to converse regularly with a guy who signed his emails "(full name), M.C.S.E.", flaunting those letters like they were equivalent to Medical Doctor or Order of the British Empire or something. Needless to say, merciless ridicule ensued.
In my humble opinion, of course.
Creative Director, Business Development manager, Creatively Directing Product Development.
Paul Blart
Mall Cop
Introduction: Full name
Sales email: Full name + "\nOwner, {{ company }}"