I'm debating whether to do a nuzlocke as well but I don't want to do it with BW given how similar BW2 is going to be. Might pick up an old version from Gamestop...
If you do, I find the easiest is Ruby/Emerald with a Mudkip.
Originally Posted by boj0
The way I'm doing it is faint = release and catch the first Pokemon in an area UNLESS it is one already in your party/box, hence the second Ratata. In which case you catch the first one you don't have. I think that makes sense.