Not so much for mistakes but has many artistic uses
There are more art products coming out these days than you can shake a paintbrush at. Some are good, but many are gimmicks. However every now and then something comes along that's really useful. The MONO Zero eraser pen, in my opinion, is just that.
Made in Japan by the Tombow company, this gadget's appeal isn't for erasing large sections, but for erasing to create super-fine highlight marks that are otherwise difficult to make. I especially like using it for sections of feathers, whiskers, fur, hair...anything that otherwise required me to laboriously work around to save the white of the paper. Eye reflections are especially easier now.
The eraser segment itself is only 2.3 mm across and akin to a white vinyl eraser. It's very gentle on most papers, as long as you keep an eye on the holding mechanism's metallic nib. When the eraser wears down, you need to click the top end to replenish it or else the bare nib can make a sharp little furrow in your work -- after which you'll pay more attention. Although it looks like the barrel itself is made from metal, that part is actually plastic, which I believe cuts down the cost. It comes with one eraser segment which can last a VERY long time. I bought refills in case I needed them, but it's been nearly six months of constant use and I'm only now getting down to the end of the first one.
If you work with in graphite with fine detail, I think this is an excellent tool to have.
If you work in ink with blubbery generalization, I think you might be better off with something else.
So far, I've only been able to find these erasers at the Schissler Academy of Fine Arts in downtown Loveland, Colorado. I'm going to check the Jerry's Artarama shop in Fort Collins and a few other places and report back. * Online they are currently found on Amazon and DickBlick.com and cost anywhere from approximately four to ten dollars, depending on shipping and handling.
* Yes, the local Jerry's does indeed carry them but are currently on backorder. I also have been helpfully informed that you can also get them directly from the company at http://www.tombowusa.com