I withdrew my earlier stylized "ac" entries as they failed my trademark test. It was close and might have been save to use, but I don't like to offer letter marks without checking "prior art" and trademarks first. There's just way to many companies and organizations with the initials "ac". Think arts council, air conditioning, (any) consulting, (any) counsel)... that last one could be scary.
I always tell people never by intellectual property from someone who's not in a jurisdiction you can sue... so... I do some research on what I'm offering.