RCON Usage?

But how do I find out mine or create one?

Well, this is somewhat complex
RCON stands for Remote Console.
RCON is for most source games that have multiplayer. Also some minecraft hosts offer RCON.
You don't 'find out yours' or 'create one', unless you have a server, then which they give you one oryou create one.
Now, for the hacking part:
I don't know for sure if you can grab an RCON password via hack, as all most all lua files are ran client side.
Here is a thread about RCON hacking, a bit edgy. [x]
According to suchisgood, if you have a Steam addon backdoor, it's possible, but I have no real response to this.
However, if you feel like manually attempting to get an RCON, just open up the gmod console and type in,
'rcon_password (password)'
I wouldn't suggest this, as most servers that are worth trying to hack have long password, usually with punctuation, capitals and lower case.

If you have any questions/would like to correct me on an error I made, please do so.

nobody will give you a rcon password getter as it most likely uses a exploit in an addon many servers have and as such releasing it would get it patched

How do i get RCON access?

give this man a medal for necroing a year old thread

*gives medal*

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Sorry ran out of medals you can have the badge in my signature if you want though.