It could be any of countless varieties, since there are thousands of kinds of peppers. However, it could be a Bulgarian Carrot chile pepper (do an image search), by the appearance and your heat description. Some people think they're very mild, but some think they're extremely hot. I saw a YouTube video of a couple guys who tried them, thinking they would be about as hot as a jalapeno. You could really tell they were in pain. The variable heat could be due to growing conditions, but there are other factors.
Another noted similarity is that they start green and then turn orange. (Many peppers start yellow; so, this is good to know.)
The only other pepper I'm personally familiar with offhand that it sort of looks like is Randy Sine's Evil Jalapeno F3, which is still not stabilized and can be orange or red, depending on which seed you use. By the look of it (from my peppers; not the picture), I would guess it's part Bulgarian Carrot, personally, but it has an amazingly good jalapeno taste (and depending on the pepper it can have next to no heat, or be super hot). With these, they go green to orange, and when they're more ripe, the orange turns a bit more yellow to my eyes. I know the picture in the link I gave doesn't look much like your pepper, but my peppers that I grew this year look similar (from one of my plants; the other plant has red peppers). Bulgarian Carrot is a much more likely match, however.