…including irrelevant crap in your signature is neither witty nor useful
When I compose an email that requires a signature block, the reason for the signature block will vary depending on the context. As I have a variety of roles, I have different signature blocks for each role.
What I do is have a TextExpander snippet (on Mac OSX or iOS) for each of those contextual roles, and then insert those manually into my email when required. And if its not required, I leave it out. When I used Windows, I would typically use ActiveWords to do the same thing (and more).
Communications (including email) should be mindful, not mindless. Put thought into all elements of your email, including the signature block.