You may have Tracker target itself with its own ability. If you do, Tracker will deal damage to itself equal to its power, then immediately do it again.

Giving either creature first strike does not affect the ability.

If this leaves the battlefield before its activated ability resolves, it will still deal damage to the targeted creature. On the other hand, if the targeted creature leaves the battlefield before the ability resolves, the ability won't resolve and no damage will be dealt.

Tracker : règles, fonctionnement et interactions (MTG)

Tracker is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

, : This creature deals damage equal to its power to target creature. That creature deals damage equal to its power to this creature.

How it works : Tracker

Original English text — Wizards of the Coast / Scryfall

#1October 1, 2009· Wizards of the Coast
You may have Tracker target itself with its own ability. If you do, Tracker will deal damage to itself equal to its power, then immediately do it again.
No other card is named in this ruling.
#2October 4, 2004· Wizards of the Coast
Giving either creature first strike does not affect the ability.
No other card is named in this ruling.
#3October 4, 2004· Wizards of the Coast
If this leaves the battlefield before its activated ability resolves, it will still deal damage to the targeted creature. On the other hand, if the targeted creature leaves the battlefield before the ability resolves, the ability won't resolve and no damage will be dealt.
No other card is named in this ruling.

Interactions with other cards

These cards' text mentions Tracker.

Cogwork Tracker

Reveal this card as you draft it and note the player who passed it to you. This creature attacks each combat if able. This creature attacks a player you noted for cards named Cogwork Tracker each combat if able.