You've had one of these people before, I know you have. The person that you just don't want to receive emails from anymore. Whether it be over an argument, disagreement, or just an annoyance, there's probably someone that you would like to just delete from your morning inbox. If it's an argument or disagreement, I'm sure you can just go on forever and ever, back and forth, just coming up with a better line or telling some idiot that they need to leave you alone and stop harassing you. You can block the person, that will frustrate them when you don't respond to their ingenious remark about you, but is that really "winning"? I think the way to really "stick it to them" would be to auto-respond to their message by creating an email filter that deletes their message while automatically replying to their message with something like:

"I am sorry to inform you that the user you are trying to send to has blocked your insignificant message. You have been deemed unworthy of sending any thoughts, letters, writings, poems, sonnets or any other literary work to this person as they are probably not worth reading and you are not worth thinking of. Please remove this sender from your address book as you will no longer be able to send to this address. Thank you".

Gmail makes this quite simple with Canned Responses and Filters:

• Create the Canned Response:
  • First craft your touting message. I like to be fairly generic so that I can re-use this message for future irritants.
    • UPDATE: You'll need to turn on Canned Responses in Labs:
      • In Gmail, Click Settings > Labs and Enable "Canned Responses" then click Save Changes
    • In Gmail, click "Compose Mail"
    • Enter a subject as well as the body of the message you want to respond back to your enemy.
    • Instead of sending this to someone, click the down arrow next to "Canned Responses" and select "New Canned Response..."
    • Title your taunt and click "Ok". This will add your new Canned Response to your account.
• Create the Filter:
  • In Gmail, click "Create a Filter" link next to the search box at the top of the screen.
  • In the "From" field, enter the email address of your nemesis. Gmail will probably auto-fill the name from your address book so you can select the name as it shows up. Click "Next Step"
  • Here's where the magic happens, check-box "Delete it" and check-box "Send canned response:" and select your taunt response from the list. Deleting it is optional at this point though. If you want to still see what the person is saying, while still making them think they are being blocked, leave the "Delete it" unchecked.
  • Click "Create Filter" and you're done! Note: Don't select the option to apply it to the conversations in the below panel as this will send a canned response for all past messages. This will probably come off as lame and will not have the same "Yeah I don't hear you" effect.