I love flying airplanes. I like everything about it, but it's the whole package that skyrockets it into love.
I'm not a machinery enthusiast, really. I trace the paths of the squirrels and marbles to laugh at Rube Goldberg contraptions. I'm impressed by machinery that does a complex job utilizing simple machines like winches and levers, wheels, cogs and screws. I like to know where the escalator goes when it gets to the bottom and why the handrails don't quite keep up to the stairs. When I was a kid I liked taking apart my toy dump truck with the toy wrench and screwdriver, and spent hours playing with those sandbox diggers with the cables and levers, but then I also spent hours crocheting hideous dolls' clothes. (Both the dolls and the clothes were hideous, if you're curious about the ambiguity there).
I have no huge affection for internal combustion engines. I acknowledge the cleverness and usefulness of the invention, and I certainly appreciate the way the parts of my engines keep on moving, hour after hour while I fly over Texas, but there's nothing else with an internal combustion engine that I appreciate as anything more than a tool. For example I would rather walk than take a car for the same amount of time, and in many cases I'd rather ride a bike than drive a car for the same distance.
I like computers. The idea of being able to parlay yes/no circuits into higher and higher commands and subroutines is interesting and disciplining. The way a computer mimics real intelligence offers insights into real intelligence. There are lots of computer applications that impress me. Usually that's not so much for the scale of how many computations they do, because I've grown up with computers and compute is what they do. I'm more impressed that someone realized that this thing that no one has done before is actually possible to do, because a computer can make that many computations and just make this work.
All of these things are part of what happens in flying an airplane, but being in command of an airplane is just something else. You put all this together and have it work for you. It's a little bit like having a well-trained dog or a horse respond to your commands, making you fiercer, more sensitive and far far faster than you are without its help. It's a little bit like being able to fly yourself. And then you feel the responsibility to get it where you are going.
I love navigation systems. Things as simple as an A-N beacon and things as simultaneously simple and complex as GNSS. I've always loved maps, especially the old ones that revealed through their crazy guesses that maps are just what we think is out there, and not necessarily what is there.
I love interpreting weather. I wrote a novel once (one of those write as fast as you can and who cares if it's any good efforts) and my friends laughed at the fact that my descriptions of the weather in each chapter could not have been written by anyone but a pilot. I couldn't write about a cloud without describing how it got there, nor have the weather in successive chapters not make sense from the point of view of frontal passage.
It doesn't matter how frustrating the customers have been, how bad the hotel, how unpalatable the food, how cold or hot it is or how cranky the ground controller was. At some point in the day I get to line up with a runway, push those throttles forward and fly! Every time the mains come off, even though I'm thinking about blue line and how far it is to the fence, and whether that Cessna pilot on the crossing runway understands what "position and hold" means, and keeping the wings level as the gear comes up, even if the gear doors cause some yaw ... every time the mains come off I also think "wheee!" I'm flying.