Why does the Torah see fit to mention "O Ben Yigach O Bas Yigach"?
Ramban #2: Because when an ox kills a grown-up, it is wicked (like a wild bear). Consequently, if the owner has been warned three times and allows it to happen a fourth time, he deserves the death-penalty with an option of paying Kofer. Not so children, who tend not to be afraid of them and for the ox to kill a child is more of a natural occurrence; we might have therefore thought that the owner is Patur. 3
Oznayim la'Torah: According to R. Akiva, 7 the Torah needs to insert this, to explain that, despite the discrepancy between the 'value' of a Katan and a Ketanah a grown-up 8 , the owner is obligated to pay his 'value to atone for his soul...
Seeing as oxen do not generally attack people.
A Safek Ben or Bas (Torah Temimah).
Even though he will ultimately inherit them. See Torah Temimah, note 233.
The ox is stoned even if there are no heirs to whom to pay (Torah Temimah).
Five Shekalim against fifty Shekalim.
Why does the Torah begin the Pasuk with the word "O"?
Ramban #1: It means literally "if it (the ox) gores a man, or a woman, or a son (a Katan) or a daughter (a Ketanah) ... ".
Why does the Torah insert the second "Yigach"?
Bava Kama, 44a: To include a Katan (who has been gored) a. by a Tam and b. by Nizakin (where the victim is wounded but did not die). 1
See Torah Temimah, note 231.
What are the implications of "ka'Mishpat ha'Zeh"?
QUESTIONS ON RASHI
Rashi writes that our verse obligate even if it killed a minor. Why do we need a verse to obligate for killing an adult?
Riva citing R"A: We might have thought that he is liable only for minors, for they do not know to guard themselves, but not for adults. Do not answer that verse 29 is needed to include biting, pushing and kicking. This does not explain why it says "Ish Oh Ishah"!