Your own Poké Ball!

[MiniMinun]

(Lol I was thinking of making a thread about this. Beat me to it!)

Some of these aren't that great, but here goes...

Magma Ball: Effective on Fire types and Ground types.

Magnet Ball: Effective on Electric types and Steel types.

Rainbow Ball: Effective if the wild Pokemon shares one type with your own Pokemon. Extremely effective if it shares two types.

Lottery Ball: (Only received from doing the ID lottery thing) The catch rate is completely random, and will vary every time you use it.

Baby Ball: (Yes, horrible name) Catch rate depends on evolution stage, with the highest catch rate being the base evolution.

Weakness Ball: The catch rate is determined based on the wild Pokemon's type weakness' (The more weakness' the better the catch rate)

These aren't really new balls, but changes I would make to old ones:

Poke Balls: Slightly more effective on legendaries (YES!)

Premier Balls: Slightly more effective on Shinies (YES YES!)

Ok, those are a little overpowered, but oh well... :)
:)

 

[Sirius Black]

Experience Ball - Gives the pokemon caught a algorithm determined amount of experience points when caught, same catch rate as a Poke-Ball and is only obtainable after the elite four

 

[Sandslash Fan]

Masuda Ball - small (1%) chance of captured Pokemon becoming shiny, or egg hatching shiny

Breed Ball - allows any Pokemon captured with it to breed with a Ditto from another region

 

[Treecko]

One of the balls I'd make
Feather Ball- Allows trainers to catch wild Pokemon, but works better on lighter Pokemon, similar to the Heavy Ball.
Catch rate:
+40 if weight of Pokemon is between 0 and 55.1 lbs.
+30 if weight of Pokemon is between 55.2 and 110.2 lbs.
+20 if weight of Pokemon is between 110.3 and 220.5 lbs.
+10 if weight of Pokemon is between 220.6 and 451.5 lbs.
-20 if weight of Pokemon is 451.6 lbs or higher.

 

[Vicktor Black]

Here is a ball for ya

System Ball - normal catch rate as pokeball but allows you with a few "limitations" to swap the pokemon inside the ball with a pokemon in your PC

 

[pokefan648]

My custom Pokeball would be Green top and Blue bottom. It would function similarly to a MasterBall, but it is called a Legendary Ball, and only catches Legendary Pokémon without failure, so if you try to catch a Non-Legendary, it will function as a normal PokeBall. It will also have a polar opposite, called the Normal Ball, which only catches normal, non-Legendary Pokémon. It will be Blue on top and Green on bottom.

 

[Hiatus]

Aside from the ones I've mentioned in my previous post, I'd also make something called "Vision Ball." If you capture psychic-type Pokémon with it, it'd help make it easier for you to EV-train. I would create "Sensor Ball" as well, which does the same, exact thing, but only for steel and electric-types. :]

 

[Aeroblast]

Status Ball (so creative): 2x catch rate for Pokemon inflicted with status.