This. Smeghead’s penis.
Dogs. What are they thinking? Why are the so eager and happy? Are they laughing?
Zippers.
Well, most everything mentioned so far is small-ish and handheld, I am going to go in a different direction of mundane - as in wide-spread use day-to-day.
Airplane - so, it weighs many tons, and is big as a building, but because it’s shaped a certain way, and can move at a certain velocity it floats through the air? Nuh uh.
Film/movie - OK, a series of still pictures, displayed in sequence at a certain speed, with or without accompanying sound, can make me happy or sad or scared or aroused or angry or adoring, etc. HUh, wow.
I think you might have offended Smeghead.
Username / post combo of the day.
The idea that I put what was once in Shakespeare’s mind into mine is absolutely fascinating. Books are magic!
Staple removers
Toilet paper
Oh, I think Smeghead can “fend for himself”, as it were. (He probably does, all the time. :D)
duct taped: two fascinating mundane things, the sum of which are greater than its parts!
Everything mentioned,aside from the penis.
Bread… So much made from so little.
Yarn… How did someone think of this?
Well, unless Wikipedia has really whiffed (always a possibility), I’m standing by my original statement. About the “needles.” I’m probably over-simplifying the electronics part of it.
I just read the Wiki article and I stand corrected sir.
Thermostats. Essentially, two small strips of different metals, bonded together in a coil, that can keep my house comfy, my water hot, my fridge and freezer cold, and not requiring any input besides one set-and-forget.
How much of modern life’s comforts depend on this little wonder? I am in awe…
The next time this pops up (and it will), you and I gang up on 'em and smoke 'em with knowledge. Righteous! 
Flying. Yea, I know the physics behind it. But I still find it incredible.
Wireless Communication. When I was a little tyke I thought it was absolutely amazing that a color TV signal could be broadcast over the air. I said to myself, “This is fucking incredible. When I get older I am going to learn how it works.” And so I did. But I still find it amazing.
Every time I go out in the rain, I’m amazed and thankful to have durable shoes that don’t leak. I’m of an age when I remember when most shoes had leather soles. Sure, boys could get rubber-soled Keds but, it seems to me, girls and adults didn’t really have that much of a choice in the matter. I remember often coming home from school with my shoes soaked through. I’m sure my brother did too, Keds or not.
I also remember Pops wearing holes in his soles, then cutting out cardboard and stuffing his shoes with it. In a choice between putting off getting a new pair a little longer and keeping his kids fed, his kids won. I’m sure lots of other Dads back then did the same.
Mechanical clocks, the kind where you can see the gears.
Microscopes.
Telescopes.
Magnifying Glasses.
Magnets.
But not Baking Soda Volcanoes!
A car magazine recently mentioned, well, cars. A machine almost as complex as an private airplane with a fraction of the maintenance.
Not something I use everyday, but very common - rocks. Amazing how beautiful even commonly found ones can be with a bit of polishing. I’ve got a jar on my coffee table of different types and people are always fiddling with them, surprised they aren’t valuable.