Guinea pigs are delicious. In the Andes, they are considered a delicacy, often served as a shish-kabob on sticks.
The downside is that they are small, and therefore there is more labor in preparing them than there is for larger meat-mammals, like cows, pigs, horses, &c.
People in times of necessity have eaten rats, and report that they are not bad.
But if one is to try rodents, why not research the large ones? I believe that the largest rodent is the capybara. It should be really good.
See: http://www.rebsig.com/capybara/capymeat.html
The capybara has white, pork-like meat, and perhaps for this reason the Vatican has declared it a “fish” (biology not being a required course in that venue!), allowable for consumption during lenten fasts.