i disagree with Jared. although i won't tell you how to Brick your phone because that wouldn't be appropriate and i don't want to get banned or something...
The main reason i disagree with Jared though is because i've bricked phones while upgrading to beta's and for other reasons that you would expect ruin my chances of getting another phone but it's not the case.
Usually if a phone is bad enough that it won't boot to anything you can just make up an excuse and they will replace it with no problem. At my local verizon store i just go in and say blah blah blah and they try to start it and see it doesn't work then hand me a new one.
Which i might do just to get back to 1.5 so i can root!!! I wanna overclock!!!!