I've been mulling this over for quite a while... and I think I'll have to say the most excited I've ever been was awaiting the births of my 3 sons. The timing between all of them made this so suspenseful to me. I remember being scared, excited and barely able to breathe. The relief of knowing that I had healthy boys, everything that I'd prayed for accentuated the excitement as well. I got to relive the excitement many times retelling my story to every person that peered in on me and the babies.
The only other big excitement for me was my travels and seeing new places and things... You just cant beat that feeling of excitement or adventure and learning.