I've prepared a few audio samples of Marshtomp's voice, which can be heard here, here, and here. I noticed that all previously implemented noises are ogg files, so I've created these in the same format.
I've pitched the sound down a bit so that it doesn't sound too similar to Mudkip's, but if it ends up being too close to Swampert (assuming you'd like me to continue making noises for the pokemon), or if you'd just rather have a higher pitched Marshtomp, I can pitch it right back up again.
It turns out that the audio quality of my mic is worse than I originally thought, but thanks to the magic of audacity's noise removal I was able to get these to sound pretty good!
Whatcha think?