Most amazing ones I've seen were in Iceland.

The only thing I've ever seen that's comparably mesmerizing and wondrous is the Northern Lights, which I saw once in Alaska.

A short aside.
A rainbow is a portion of the base of a cone. You (the viewer) are (at) the apex of that cone. If one moves the apex by the slightest, a different segment of a different (circular) base is observed as a rainbow. That means that two people standing ear to ear, eye to eye, are viewing, literally, different (unique) rainbows!
No two people see the same rainbow.
And, as we are the 'apex' of the equation, it is us that is the metaphoric 'pot of gold' at the 'end' of the rainbow!
Now the secret's out!

... I share your enthusiasm - I go out chasing them every chance I get ...

One time I had been running, and on my way home I saw a beautiful rainbow which ended on the small church. It felt magical, but didn't made me anymore christian. Maybe it should..

The light of a rainbow vanishes, not the light of God . A rainbow is a fleeting sign.

Just so that everyone is forwarned, a pot of gold does not always exist as the end of the rainbow, I know this both from intuition (why would there be?) and from experiance. Yes that's right, we managed to create a minature rainbow using a hose, I tried to stand at the end of it, and indeed it looked from my friends' angle that I was standing there in the wet, with a rainbow sticking out of my chest. But for my part as soon as I walked towards it, it disappeared (due to light/angle etc) so it looked to me like I was standing there in the wet for nothing like a complete fool, hehe. No, there was no pot of gold, I was very disappointed.

Rainbows are nice, but I think the most beautiful thing in the universe is Nebulae. They are fascinating...saw a show on them, and different types of stars, and galaxies in high def a while back. Hope to see more soon.

Neil