Really couldn't say to be honest, I like so much. My current favourite is probably Muse though I love Radiohead and a lot of older Classic Rock (the Stones, Hendrix etc); I'm not really that discriminating.
I like Nirvana too Ben

. My personal fave is
In Bloom though the songs you mentioned (
Teen Spirit/Come as You Are) are great too. My least favourite is probably
Heart Shaped Box though inexplicably I still have it on iTunes...
As for favourite song ever I'd have to say either
Freebird by Lynyrd Skynyrd (always have to check if I spelled that damn name right

) or
Little Green Bag by George Baker Selection (yes the Reservoir Dogs one...), though I have also grown quite attatched to
Supermassive Black Hole, Knights of Cydonia and
Time is Running Out by Muse lately too.
Uhh yeah I think that's it. Apologies if I bored you with my extreme rock nerdiness.
And Ben if you ever want to drone on about Nirvana for hours, just talk to me

.