I was inspired to google "the largest rat in the world" and was interested to see it is the African Gambian Pouch Rat. What is more interesting is that these beasts were introduced into Florida a few years back and are running wild in the Florida Keys, eating everything in sight.
A further search uncovered the following charming wanted-ad at http://www.hoobly.com/0/0/37281.html:
African Gambian Pouch Rat
I am looking to adopt a gambian pouch rat, Or any information on adopting one, also I am looking for a large cage.
That better be a large cage. Those guys get about 17 inches in length. There's an old saying in Key Largo, that when you hear thunder, that is God rubbing two Pouch Rats together.
For more info on these things, visit: http://www.allianceforamerica.org/bb/viewtopic.php?p=3036
I am not sure what the Alliance for America is about, but I know they are rabidly anti-African Gambian Pouch Rat.