How can I kill my own internet without getting out of my chair?

Teamviewer does a nice job at accessing other PCs.

depends if its a wired or wireless network really

for wireless you can setup MAC filtering, and create a list of allowed computers that can connect, and just remove them from the list if you don't want them connected any more and add them back when you do

not sure on what to do for wired, other then disconnecting it from the router

Log into the router, set a manual static IP of something random. It'll kill the whole internet since your router won't get the right IP from your ISP.

Depends on what router you have. Custom Firmware allows you to do quite a few things

Enable QoS and regulate other PCs traffic so it goes snails pace
Completely block certain protocols like FTP or HTTP
You could also enable printer sharing and print a bunch of blank pages in Excel (used to do this in high school, cant believe they never found out which computer it was coming from)
I think windows has a network messaging thing. You could send random messages to other PCs.
Theres always Remote Access

the problem being I don't have the password for the router right now so everyone uses a cat5 or cat6 cable

unhook the ethernet cables?
Hammer the router?

Lets not talk about Denial of Service attacks in a malicious way, we can't be rationalizing or making it acceptable to boast about doing these to prior websites.

On topic, you could always reboot the router using a telnet or ssh command, or just from the GUI. You could log into your modem by using 192.168.100.100 or googling the manufacturer and model number for information and reboot (NOT RESET) for that.

ill reset it, get the pword, and try some of these.

Check out an application called NetCut. You can cause absolute misery for your fellow networked users. But I guess you don't really want to do that. Eh!

You can use it to prevent people cutting you off, also.