First textbook example: nominative

The Rule of the Muʿrab: Visible and Estimated Case

جَاءَنِي زَيْدٌ
Translation: Zayd came to me.

Parsing
جَاءَ: past-tense verb, built on fatḥ.
نِ: protective nūn before the first-person suffix.
ي: attached first-person pronoun, in the accusative object position.
زَيْدٌ: subject, nominative, with an overt ḍamma.

Why?
Zayd is the one who arrived, so the noun is the subject. The ḍamma on the ending is visible.