Fuck Jack Thompson. Incase you don't know who Jack Thompson is, he is the anti-christ of the video game world, trying his best to remove every single good video game from the market. He also likes big fat cock rammed up his ass.
And according to the above, it is safe to say that Jack Thompson is the cause of everything evil and malicious in this world, therefore, using his name in vain is a perfectly acceptable way to relieve stress.
Example of FJT:
The damn microwave broke! FJT!
I can't believe this is happening to me! FJT!
Example of the name in use:
You crashed into me, you son of a Jack Thompson!