Most exciting? I'd say the first time I had a REAL close encounter with a buck. I'd just started archery hunting, no mentor, just trying to figure it out myself.
I heard running behind me...I turned around in my treestand & saw a big 6 pointer standing behind me, maybe 10 feet away, stopped & on high alert. I froze, but my knees & hands wouldn't stop shaking. I knew enough to not make eye contact, so I turned around slowly, somehow managed to nock an arrow, & got ready for him to move closer & give me a shot. After what seemed an eternity, he came around my tree, this time directly underneath me. He never did turn broadside, just wandered off munching brush with his tail facing me. I tried the doe bleat, didn't faze him. I would say it took a good 20 minutes for me to gain my composure & figure out what had just happened.
I've had numerous encounters like this since (and occasionally score), but this had to be the most exciting.