Okay, for reals:
Heavy industrial construction, especially as it relates to steam-powered electric power generation: coal-fired, oil-fired and nuclear steam power boilers; industrial power and recovery boilers, and related issues. (Surprisingly, though, I know very little about “electricity” itself; it’s still mostly magic to me.) As a general rule “mechanical workings in general” I can generally suss out, even though I don’t often work with tools any more.
Sailing and related arts, including rope and wire splicing, knots and their suitability for various applications (not so much BDSM, but I’m always willing to learn or experiment).
Reading, writing, spelling, grammar, vocabulary, words in general and wordplay when I’m in the mood for it.
Interpersonal relationships: since I’ve had so many and such varied relationships I understand what motivates people sometimes, in ways that seem obvious to me but are clearly not obvious to others.
Microsoft Excel and Access, including Visual Basic for Application (VBA), macro creation and user-defined functions (and how to find resources who really grok that stuff). The more advanced my computers become, however, the less I understand about how they really work.
History in general, and history of the latter half of the 20th century in particular – since I lived most all of it, influenced it in tiny ways, and even recall some of it.
Entrepreneurism, since I am incredibly proud to have influenced my daughter to start her own business, which even after her first year was a thriving success, and now near the end of her fourth year, has literally doubled from a great start.
Libertarianism (small “L”) and “freedom issues” in general. My guiding principle when attempting to determine which of various proposals for government is best, or “better than some other” (in the abstract or in terms of actual policy) is the answer to the question “Which one increases liberty?” Regardless of what any proposed (touted) benefits are breathlessly promised “to everyone”, if the proposal in question decreases personal liberty, then I will be opposed.
Oh, and sex. I still remember that, too.