What do you use your master ball on?

[The name master]

Self-explanatory.

I used mine on moltres in Leaf Green today.

I always use it on Latias in Emerald/Sapphire.

[sans the skeleton]

i dont tend to use mine. i prefer catching them with pokeballs. only exceptions recently have been raikou (caught bc i just wanted him and didnt have a catcher pokemon) and other dog legends.

otherwise i keep them on standby as i look for shiny legendaries or whatever

[The Hooded Trainer]

Back when I was a stupid kid and I didn't understand stuff, I kept using them on regular pokemon whenever I ran out of pokeballs. Now I'm pretty much the same as poison, saving them for shinys that are too difficult to catch otherwise. Thinking about it though, I'm not sure if I've ever used a master ball on a shiny, so I've probably still got a couple stashed away in most of my games.

[Pam-the-Lamb]

 I try not to use mine since there's only one but during my AS playthrough I used it on Papa-D since I couldn't be bothered to go through the cutscene again and I didn't have any left.

Almost exclusively use Pokeballs with Ultra Balls reserved for legendaries. I find a lot of the other ball designs really ugly so I just keep everyone in the originals.