Spiritual Gifts: Number

Just how many spiritual gifts are there?

In my reading, I've come across many answers to that question. It really depends on how one answers some key considerations, such as:

What biblical LISTS are listing spiritual gifts?
What biblical non-list verses mention spiritual gifts?
Are there 'extra-biblical' spiritual gifts?

A related question, which we will deal with separately, has to do with whether some of the gifts are actually duplicated in other passages while using slightly different words. For now, however, I simply want to share my thoughts on these 3 important questions.

What biblical LISTS are listing spiritual gifts?
There are many lists in the New Testament. For example, there are lists of apostles, lists of virtues, and lists of vices. There are also, indisputably, lists of spiritual gifts. What is not indisputable, however, is which lists belong to this collection. The most common understanding is that the lists are found in Romans 12, 1 Corinthians 12, Ephesians 4, and 1 Peter 4. I find this quite agreeable (with one caveat that I will mention in answer to the 3rd question).

What biblical non-list verses mention spiritual gifts?
We should not trap ourselves into thinking that all spiritual gifts must have been mentioned in list form. There are some spiritual gifts (usually using the same Greek word(s) for gift) mentioned in isolation from the bigger lists. There is debate on most of them as to whether the biblical authors intended them to be considered as spiritual gifts, but in most cases I find no reason to reject them as such. Some of the suggested additions would be gifts like hospitality, singleness, marriage, vows of poverty, martyrdom, music, and craftsmanship. My inclusion of these will make even more sense in light of my answer to the third question.

Are there 'extra-biblical' spiritual gifts?
I don't see why not! We have no reason to believe that Paul, for instance, was attempting to compile a complete list of spiritual gifts. Indeed, we have plenty of reason not to believe that (since each list contains both overlap and distinction). Paul included examples, perhaps picked especially for the recipients of each letter. There are probably lots of 'extra-biblical' gifts. This is why I have so willing to accept non-list gifts and (to fulfill my promised caveat) the lists from the controversial ending of Mark 16 (whether it is original or not, there are no good reasons for rejecting its list of sign-gifts).

Answering these questions in these ways will make it impossible to do a COMPLETE study of the spiritual gifts, but that's OK. My only aim is to do a helpful study.