Note: This wont work on official servers nor will it work on all of the other servers. If the server you try it on have some kind of command restriction it wont work (if it only allows you to send a limited amounts of commands per second).
Anyway here's how you are able to create a ton of lag without any third party program (or downloading gigatons of files)!
Open up the console and write;
Code:
bind <INSERT SOME KEY HERE> "status;status;status;status;status;status;status;status;status;status;status;status; < just repeat 'status;' some more >"
For example, you could bind it to both scroll up and scroll down like this:
Code:
bind mwheelup "status;status;status;status;status;status;status;status;status;status;status;status;status;status;status;status;"
^ That was scroll up, now for scrolling down;
Code:
bind mwheeldown "status;status;status;status;status;status;status;status;status;status;status;status;status;status;status;status;"
Then just spam the selected button and create huge amount of lags! This could be used to do things such as make you harder to kill or letting you peak without people actually seeing you.