This is one of my favourite Nirvana songs, and I play it with my band all the time. It was never released, but that slut Courtney Love decided to let it out in the open after Kurt's death.
There aren't any correct tabs for this song yet, but because I've matched mine up with the correct guitar tabs, and I've played it 1 million times before, I'm 100 per cent sure that this is right. 
It's really easy. All u need to play is

Verse and chorus
G
D
A  2222      5555
E       3333      2222

Bass solo, (with just drums and no guitar)

G
D
A  222     555
E      333     2222

For those who would prefer, the notes used are B, G, D and F sharp

That's all there is to it. It's pretty easy!
Long live Kurt Cobain
Grunge will never die!