Answer: The grammatically correct sentence would be "I wish I were taller, so I could dunk on all my basketball teammates."
Explanation: The verb "wish" is what is known as a "subjunctive" verb. This means that it is used when we talk about things that are not necessarily true or real. When we use the subjunctive form of the verb "to be" with "wish," we use the word "were" instead of "was" regardless of the subject of the sentence. This is because "were" is the correct subjunctive form, while "was" is the past indicative form. Therefore, the correct sentence would be "I wish I were taller, so I could dunk on all my basketball teammates."
Hope this helps, and have a great day!