I thought that Cardsox's format for the last SOK was really great, so I'll be doing the same type of list today, with a little bit of a difference.
Alternative:F.C.P.R.E.M.I.X.-The Fall of Troy
You may have heard this song on Guitar Hero, to which I say FU. It pisses me off when people only here a song through that game(although I do enjoy all of them tremendously). Fantastic guitar picking in the beginning, and a sweet video(watch the drumstick twirl!)
I don't know much about rap, but I know this is a great song. It features Black Thought and the great Talib Kweli.
These guys aren't true metal per se, but that's where they fit closest. A friend introduced me to them recently, and I cannot recomend them enough. Extremely talented musicanship and good range. I tried to find a song that had this sick bass in it, but I'm not sure what song it was. So here you go.
If you can't stand listen to hardcore vocals, at least skip to the 3:25 mark. There starts an insane breakdown with the fastest double bass drumming you'll hear.
How about some piano music to cleanse the palette? It may surprise you to learn that I love this song. I think the lyrics are outstanding, and it really is a touching song. Great, now I sound all queer.
It blew me away when I first heard of this band that THIS ^ guy is a great reggae singer. This is another song I've been into lately.
Justice is a very cool electronic dance band from France. This video is very cool as well. YAY VIOLENCE!
Nineties: Tommy the Cat-Primus
One of the weirdest bands of the decade is also one of the greatest. Les Claypool is pretty much the greatest bass player ever. You should check out the live version of this song from Primus Sucks for his bass soloing.
Eighties: Danger on the Track-Europe
Yes, Europe is pretty much my guilty pleasure band. Everyone knows the Final Countdown, but a large amount of their songs are in the movie Hot Rod, which is where I heard them. This is one of my favorite songs now.
Comedy: Jenny-Flight of the Conchords
This is going to sound lame, but my new favorite band of the moment is Flight of the Conchords. I just recently started listening to them and everything they do is brilliant. Here's an epic song about mistaken identity.
Also check out: The Valley. I wasn't able to find any good videos of this band, so they were left out. They're a mix of nineties alternative and hardcore. They sound like Nirvana sometimes. Check out the song, "Come Down."