I bought a new Asus RT N16 router today. I am going to load Tomato USB on the router. If I brick the router during this process, do I need any extra hardware to unbrick the router? I read somewhere that you need to connect to the router using serial cable to unbrick some routers. Is that the case with N16?
Yes, I can't tell for your model or the router software but I have a Linksys Wag200G and sometimes I use a special serial cable to unbrick the router. It's not very often but it's extremly useful to have it. Here is some link about JTAG interface and cable:
You need to buy some cheap electronics and solder. Disclaimer: You need some experience with soldierung it's very likely you brick your device. I've bricked one Linksys WAG200 by wrong soldering and also I think you will loose warranty and so on. Do it at your own risk!