Often traveling in packs, rats are usually the first enemy fought in RPGs.
Almost all video game rats are hideously over sized, and only sometimes correctly identified as Giant Rats.
One of the primary reasons why rats are featured so prominently in RPGs is so that a starting player can have an enemy that poses little-to-no challenge so that the player can learn the basic game mechanics. This concept has proven to be effective, as many games have incorporated it into their products to the point that it has become one of the greatest cliches in the gaming industry. They are amazing creatures indeed.
They are often encountered in RPGs as the first enemies due to the cliche that the player has to escape a horrible fate through either a sewer system or deep underground tunnels.
Mainly used for foraging these creatures have tails that act as radar for food sources, often coming back to food stores several years later.
The term "Rat" Is also used in many MMOs for respawning mobs that are easy to take out and gain items and money from. Many times these "RATS" are spawn killed over and over to gain said money and items quickly.