When Do You Use Your Masterball???

[Trainer Gabriel]

On either the highest level Pokemon in the game or roamers.

 

[ShinyEevee]

Haven't used one since Gold although I'd use tf if came across a shiny that teleports, explodes etc.

 

[xxxthebxxx]

Usually just on the roamers. Thankfully Black/White only had one, so it was easier than Platinum with its 5 roamers!

 

[Stuntology]

Always on the roamers. I don't have the patience to catch all of them in every game. I just wish I could transfer my 2nd masterball from white onto heartgold, where there are actually more roamers than master balls.

 

[Adachi]

I don't use my Masterball, unless I run into a shiny that can kill itself!
Otherwise, nope, I will keep it forever in my bag.

 

[Sir Turtlelot]

I used to save it for either a high-level pokemon, like Mewtwo or Rayquaza, but anymore I use it on a roaming pokemon. I hate those. A friend of mine decided to restart his version of Black, so he agreed to let me have Reshiram and Tornadus. The only problem was he used his Master Ball on Reshiram and hadn't caught Tornadus. After several days of running in grass and cursing, I finally caught him.