It is annoying, I recently annoyed the hell out of a fellow passenger, he was kind enough to request to change his seat in a polite way and that's when I noticed. I was totally unaware of the fact that I was annoying him at first, and I wasn't playing games, which I assume would have generated more clicks.

I am no fan of trackpads and I have a small mouse that I use on top of my laptop (next to the trackpad) due to the small space of the tray at economy class, this little mouse have very loud clicks.

After the flight I have googled "quiet mouse" and I found a few choices of mice designed for this specific case -- to avoid bothering others. I haven't picked up one yet, so I cannot recommend a specific model.

While as others have rightly pointed out it may depend on your hardware and your neighbors, I think it's also worth noting it will depend on the game.

If you're playing a high-intensity first-person shooter and hammering the mouse buttons (or indeed the keyboard, and moving the mouse with high intensity) then you're more likely to be a nuisance to those around you than if you're using the same hardware to play correspondence chess.

In either case, the clicks and taps you produce will be of comparable volume to other socially-acceptable behavior associated with surviving comfortably on a flight, but those other sources of noise are generally sporadic (and the acceptable threshold will vary between phases of the flight depending on whether meals are being served or the lights are dimmed for sleeping). It is the patterns in your clicking established by the game that are most likely to transform the clicks into an annoyance.

If in any doubt, your immediate neighbors will almost certainly be happier if you ask if they mind first or invite them to tell you if you're disturbing them.

That depends on the plane, the neighbors and the mouse. Some ideas:

• https://thepointsguy.com/news/quietest-aircraft-in-the-sky/ gives some measurements of airplane cabine noise level, which you could compare against the decibel level of your mouse clicks.
• How can I reduce the sound of clicking my mouse contains a few ideas on how to reduce the sound of your mouse clicks and a pointer to a quiet mouse.
• For mechanical keyboards, use o-rings to reduce the sound.

How much of a douche will I be if I bring a mouse (wired) with me?

Not at all a douche. Don't sweat it.

Laptops have been commonplace on flights for 20-30 years. The noise of a keyboard or mouse is very low, even for the person right next to you, and is accepted as being a normal part of mass-transit transportation in the same way as the noise of turning pages on a book or magazine. Unless you're playing a game which requires you to mash buttons very fast for a long period (like 1980s sports games), this just isn't an issue.

What you do need if you're playing games is a headset with minimal leakage. That's noise which no-one wants to hear. Ideally of course play with sound off.

Frame Challenge: you won't have room for your mouse.

While not all airplane tray tables are the same size, they are generally about 16" wide. The most compact gaming laptops are still about 12.5" wide, with the next biggest size being around 14" wide. Now, unless you choose to bring a trackball mouse as recommended by manassehkatz (which aren't exactly ideal for gaming either), you won't be able to fit your mouse in that 2-4" gap.

Also, if you choose to go this path of gaming on a plane, make sure your games and laptop are fully patched and configured to work without an Internet connection. Internet on a plane is slow both in ping and throughput, expensive and unreliable, so you're better off not relying on it if you can help it. And be on the lookout for turbulence, which may risk throwing your laptop in the air if you're not careful.

I wouldn't be concerned about the noise at all.

However, I'd highly recommend a trackball instead of a mouse.

Trackballs are a lot less common these days than mice. But in addition to being, IMHO, far better for your hand & wrist, they don't take extra space the way a mouse does. That isn't a big deal with a regular desk. It is a huge deal when you are using the extremely limited space of an airplane seat.

For those who are not familiar with a trackball, in a sense they are like an upside-down mouse, where you move the ball instead of the whole contraption. Except that mice haven't had a physical ball in many years. I prefer the Logitech M570 but there are other models available from Logitech, Kensington and other companies.

Assuming you mean action competition-type games,

the answer is obviously "Of course that's annoying and you can't do it."

Note too that you can't, anyway, really have on a large bright laptop (say, to watch a movie) during sleep periods, unless you're a 'not nice person'.

(You mention Biz/First. You can do what you want in 1st as there's plenty of room/privacy, nobody will hear or see. Re business class, it varies a lot.)

Sure, you can sit there and quietly play Rail Tycoon or the like.

But you can't "game" in the sense of "The games played by Korean professional teams!" on an airplane, it's just silly. Of course not.

Note that the same applies to people who work on laptops (in economy). Sure, you can sit there and read some documents, etc. But anyone who furiously types for hours (in economy) is a 'not nice person'.