During one of my visits to Pen Boutique's Columbia, Maryland store, a salesperson there mentioned a disposable fountain pen. I couldn't imagine such a thing so it piqued my interest. It turned out the pen the salesperson was talking about is Pilot's Varsity fountain pen. Pilot's pen comes in 7 colors (black, blue, green, pink, red, purple and turquoise). It has a small window on the side of the pen where you can see how much ink the pen has left. The pen in my opinion is very reasonably priced. I paid $3.25 for one at Pen Boutique and, Pilot sells them for $3.45 on their website
http://www.pilotpen.us/Default.aspx Nib wise, I believe it has a medium nib and, this is the only type of nib you can get the pen in. The thing that has most impressed me about this pen is how smoothly it writes. I've found that stainless steel nibs seem to scratch the paper when writing. Till I tried Pilot's pen, the only nibs I'd found that glided across the paper well were gold plated ones. The Varsity pen obviously isn't gold plated but, it does write really smoothly. In my opinion, Pilot's Varsity fountain pen is a really good cheap fountain pen that happens to be disposable. If you like writing with fountain pens, I think you'd be pleasantly surprised by this pen. Happy writing all.
Update September 18, 2016: Recently, I bought some more of these fine pens and, here is some more information on them. First, Pilot has changed the outward appearance of the pens giving them a sharper appearance with the Pilot and Varsity names. Also, the pens have a diamond motif on them vice the previous lines that ran length wise on the main part of the pen. The pens still write really well.
Price wise, Walmart is offering a really good deal on a 7 pen multi-color pack on their website. I was able to buy the pack for $13.05 which breaks out to less than $2 a pen, a big savings. Their normal price is $14.35 which is still way better than if you bought the pens one at a time. Also, Walmart will ship the pens to a Walmart store close to you for free if you can't place an order over $50 (which I believe qualifies you for free shipping). Also, Walmart participates in the MyPoints rewards program so, you'll earn MyPoints with your purchase as long you use the MyPoints link to the Walmart webpage. I forget how many points you'll earn per dollar spent.
If you want to buy the pens one at a time, you might want to buy them from Pen Boutique as they sell them at their Columbia, Maryland store for $3 each or $3.37 on their website.
Correction: I found out I had the price wrong for the pen at the Pen Boutique website. It's $3.37 per pen (as of the date of this post) vice the $3.33 I erroneously quoted when I first posted this update. My apologies. The error has been corrected.