How many words for I are there in Chinese? I wonder how many words and pronunciations for I exist/existed in Chinese. 

I know of these:

我：wǒ， but I believe it is pronounced ngo in Cantonese. 

There seems to be an n-root for I in Chinese. I know, in 江苏泰州话， I = n

吾: wú also yù

余：yú

俺：ǎn （孙悟空说的“俺老空”）

Can you contribute any more Is， please?
I would like to share an interesting “I”, 朕. 

In modern day (or post-Qin Dynasty) usage, 朕 was a first person pronoun reserved solely for the Emperor to refer to himself in front of all his subjects. 

However, before the Qin Dynasty, 朕 was a word used by all commoners to refer to themselves, among the large variety of words which conveyed the same meaning. (予、僕、吾、我）

屈原, who lived in the Warring States period of the Zhou dynasty, wrote a poem called 离骚. The first line says:


  帝高阳之苗裔兮，朕皇考曰伯庸。


“(I am) a descendant of 帝高阳, my (late) father’s name is 伯庸.”