what are the best testament songs?  

return to serenity is a good song! you should try and listen to it. basically, all testament songs are good. its like a heavier version of metallica. but of course testament is better in my opinion. here are some of the good songs : trial by fire, low, sewn shut eyes, and many more!

oh, i dunno what song to give you, but "First Strike is Deadly" and "The Gathering" Album is the best for me, all the song on it is good ^_^ check it out XD

Into The Pit is an awesome one and everything off the First Strike Still Deadly album