What should I do if I end up without an adviser? I am a 2nd year PhD student and I have passed all prelims. However, I am facing a problem: I may not be able to get an adviser.

There were several potential advisers I was trying to approach. One of them suddenly left, others are either "do not know anything about my topic", "too busy to take a student", or simply ignored me at all (It seems that they were always not in their offices, and they simply ignored my emails.)
And now I have trying my last shot on one of the faculties, but it seems that (s)he is not willing to take me and (s)he claimed that (s)he may not be a good adviser.

I talked with my friends and we got possible solutions. However, I am not sure if they are good or possible. So I would like to get some advice here:

(1) Switch field:

(I tried approaching all faculties with similar interest.) The problem is I know nothing about their fields and I didn't take any basic courses related to these fields.
So the two problems are:
(a) I know nothing, is it too late to start over now?
(b) To be honest I am not interested in these fields. However if I stay here I think I need to switch my field probably. Is it really a good idea because I may need to face something I don't like for 3 to 4 years.

(2) Staying in my school and try to get an adviser elsewhere:

Is it hard to do so given that I am not a brilliant student? Since they do not have the burden to take a student from somewhere else.
If I approach them, how should I explain my situation? Since there are some faculties working on my field.

(3) Transfer to another school:

If I am going to apply another school, how will they think of me? Will they think I have no adviser because I am dumb? Or will they think I may end up without an adviser again?

Also, in general, do I have to restart everything again? (Including the prelims.)
I know that some schools will force their student taking the prelim courses irrespective to their background, in this case, I think I will waste time on the same material.

[Added] And one more problem for (3) is I doubt I can get 3 reference letters again...[/Added]

Finally, is it good idea to reapply those school who accepted me before?

Do you have another possible solution? And how do you think about these solutions? And if it is field dependent, do you mind indicating which field you are talking about?

Sorry about my poor language and thanks a lot.
I think that your best option is the first, but that is based on my personal preference and may not be yours. So let me explain. 

Many students choose an advisor late and are then guided by ideas of the advisor. There is nothing wrong with that. 

Finding an advisor at another school will cause lots of complications both in the short term and in getting everything finished up. 

Moving to another school may not find you an advisor for "your topic" in any case. It will require a new advisor. 

As a student, your short term goal is to get a degree and then move on. There is nothing to prevent you from then going back to your original ideas and developing them. There is nothing but time and hard work to keeping your hand in on those ideas so that you don't get too far out of the current loop if the topic is popular. 

To expand on the first choice, I would choose a highly regarded advisor who has a lot of ideas. Work with him/her on something that is as close as you can get to what you really want to do, but, primarily, work to finish and move on. Your career will last beyond your student days, but you have to get there first. 

I didn't have an advisor (in math) until about your stage. 



I'll note that there is another option that may be open to you. I mention it for completeness, but it is a difficult path to follow. Some students work without much of any advice from an advisor, being very self directed. They need a formal signature and some letters at the end, but the behavior during the course of studies is more like that of a colleague, rather than as a student. You need to arrange this sort of relationship in advance, of course, but it works for some.