I tried to get into Mastodon a few years ago but they didn't do anything for me.
My vote here is gonna go to Worship Music here. Anthrax is one of my favorite bands ever, Joey is back and they have great new album that has a good variety of metal songs for everyone.
Dystopia is a very close second though. The title track alone makes it a worthy album of the year canidate. Honestly, if you're a fan in anyway of old school sounding metal and you don't like Dystopia there might be something seriously worng with you
Thriteen is like four good songs surrounded by a bunch of garbage. I know they wanted out of their record contract ASAP but they could've waited until next year and made something a bit better. As it stands this album is right at the bottom of Megadeth's list between TWNAH and Risk.