Seeing my boyfriend for the first time in months (he lives 500 miles away from me). I had been dealing with anxiety attacks since I'd last seen him and being with him was the ultimate high/relief.
Waking up one morning after a few weeks of grain elimination and increased fat, vitamin & mineral consumption (not yet entirely paleo!) realizing I didn't feel nearly as anxious, depressed or lost as I had weeks prior.
Waking up one morning after a while on paleo realizing I didn't have any symptoms at all of anxiety or depression, I had an appetite, and I was actually happy for no apparent reason.
On that note ^, being able to dance again after months of inactivity related to anxiety.
Holding my niece for the first time hours after she was born--on 9/10/11 :D
Go-go dancing on stage for one of my favorite 60s bands who'd recently reunited
for me, it's often related to breaking through fitness barriers. Fight Gone Bad was definitely up there for me. Also, getting my first unassisted pullup.
Also, a different kind of peak experience often comes to me when I run. It's not like a sharp high, but more like a serenity and peaceful joy. And that often comes to me when I'm running and it's easy, and I feel like my body is doing what it was meant to do, and I'm so darned grateful that I feel like crying.
I don't need to do anything special to be happy. By following Paleo, and especially Paleo-ketogenic (which messes with the brain more than plain Paleo does), I'm happy all the time. I explained about all that here: http://eugenia.queru.com/2012/03/07/bliss/