I was recently on youtube checking out the awesome STAR_ when I came across this video with TF2 shenanigans where he put in some console commands to add in the valve rocket launcher and other weapons (eg Robin Walker's Rocket Launcher). What is the console command for this? Thanks!!!
Short answer: extensive modding and customization, and a server that can handle all of that.
Personally, I haven't experimented with this, but there is a tutorial that explains how it was done. Looks very interesting but not too difficult, however I don't know how this would affect VAC bans and such, so use at your own risk!