Hi It looks to be an Anaheim Chili Pepper. I googled and found a place selling plants as 'Anaheim Chili Red' hot pepper so that maybe where the name came from.
Remy

Here is a link that might be useful: Anaheim Chili Red Hot Pepper

Thanks, remy. I called the company that sells the plants (bonnieplants.com), and the customer service manager there told me it was a cow horn pepper plant (linked below). I'm hoping it's either that or the Anaheim pepper, as you've suggested, because I'm wanting to stuff them, and a cayenne would be too hot for this. In the link, that pepper sure does look like the one you linked. This is confusing me.

Here is a link that might be useful: Cowhorn pepper?

Cayenne peppers are generally too small to stuff anyways.

I'm trying a few "Corno di Toro" pepper plants this year which I'm guessing might be the same as your "cow horn" pepper. You may wish to look for this name as well if you are looking for seeds.

FataMorgana

Here is a link that might be useful: Google Images - Corno di Toro

I did a little googling and it seems Cowhorn peppers aren't really cayennes, and Cowhorns are mild to medium hot like an Anaheim. So what ever it is, it looks like it will be a good stuffer.
Corno Di Toro (Bull's Horn) are similar looking, but sweet with no heat.
Remy