My most memorable moment was also the most rewarding moment. My girlfriend and I waited in line for nearly 16 hours in Dallas, during the spring of 2001, to get front row in the "heart".
I touched Bono boot (LOL...I felt like I was touching the shoe of Christ), touched his hand ((sighing)...Kafka-esque experience) and felt his sweat hit my forehead.
Later, we held up a sign that said, "Please play PLEASE?". The Edge saw it and chuckled, shook his head and non-verbally expressed regret about not having rehearsed the arrangement, or something to that effect.
My second most memorable moment was when I heard "With or Without You" for the first time. I stopped playing my video game when Bono reached those high notes toward the end. I couldn't believe what I was hearing, so I rewound the song and listened to it over and over again until I knew it by heart. I've been a U2 fan ever since.