Cobain and his Martin D-18E, a left handed one.

That the music of Nirvana changed the music scene when it became popular in about the year 1993 is unquestionable.  That Nirvana was most often a heavy hitting electric band full of screaming guitars, vocals, and thumping drum and bass rhythm section is also simply fact.  The very last album by the band which put grunge music on the map, however, was an all acoustic album.  MTV Unplugged In New York was that final album[1], and that is where Nirvana left us forever, with a brooding, depressing, beautiful acoustic album.

While the unplugged genre of live albums was becoming a thing rather popular for otherwise plugged in bands or artists to do, it was also something which allowed us to see such musicians were actually capable of playing in other formats.  There's really a bit of a transition to deal with for a guitarist when switching from electric to acoustic guitars.  Oh they're the same instruments, but the acoustic variety of guitar requires the use of much bigger strings, and those put a lot more stress on both the picking or strumming hand, and especially the fret board hand.  Kurt Cobain, however, was always primarily a rhythm guitarist on either electric or acoustic.  

The MTV Unplugged In New York album by Nirvana would prove to be their swan song.  The music was mostly a mix of tunes which were written by other artists, and a few of the band's own lesser known songs.  It gave us all a new way to think of those three musicians we thought we'd known so well, and a chance to literally hear what it sounded like for Kurt Cobain to say "goodbye" to us all.

Kurt Cobain And The Martin D-18E Guitar

So What Exact Guitar Was Kurt Cobain Playing In The MTV Unplugged Concert?

Answer: Cobain Played The Martin D-18e

The live acoustic album by Nirvana, their final album, sounded terrific, and it still does.  While it would be near impossible to duplicate the emotional vocals and quirks presented in the show by Kurt Cobain, what isn't impossible is to have the same guitar as he had.  The guitar is a Martin D-18, one of the most admired and famous acoustic guitars in the world.

The exact year of Kurt's D-18 is 1958, and this guitar is extremely rare.  This guitar, with three pickups on it, isn't something one is ever likely to come into contact with; and so it is a very collectible instrument.  The three pickups are two DeArmonds pickups, and one Bartolini pickup. It is rumored that during the MTV Unplugged concert, only the Bartolini pickup was working for Kurt. Another thing which is perfectly obvious from the images is this specific instrument is a right handed model.  Kurt Cobain was a left handed guitarist, and so he simply flipped the stringing of the instrument around to where it would be normal for a left handed musician to play.

I'm told Kurt's setup was stomp box distortion pedal ran into a Fender SF Twin Reverb amplifier  The thing most important to note here is that the 1958 D-18e was a very good acoustic guitar with very old and not so wonderful pickups on the thing.  If someone wanted to achieve a sound comparable or even superior to what Kurt had achieved in the Unplugged In New York concert, they could do so with a much less expensive and more modern instrument with modern pre-amp and pickups on the thing.

 So far as alternate guitars built to Martin D-18 specifications but sold at a far more reasonable price goes, I will forever and ever advise one to purchase a Blueridge BR-140, which is an absolutely terrific Chinese version of the D-18 and is all solid wood, built to Martin specs, and can be purchased brand spanking new for less than six hundred dollars.  There are other fine alternatives instruments as well.  No one should mistreat a D-18 by putting pickups onto it unless they're just that willing to be disrespectful to something so wonderful as a D-18, and so unworthy of abuse.  There are many a fine mahogany body Alvarez, Yamaha, and Takamine instruments out there available new or used where one can either purchase with the electronics, or without the electronics and then add the most modern ones available for the best possible sound. Outside of the mahogany body steel string flat top dreadnought design, the most important things to consider for replicating this Nirvana tonality of the unplugged variety would be the stomp box distortion pedal and the Fender SF Twin Reverb amp.   

Now Here Is the ENTIRE Nirvana Unplugged In New York Concert

With that terrific D-18 Sound!