I didn't know giants were even dangerous, unless you attacked them, until level 63 on my first guy. I was just running past another giant, this time with my weapons out, and I just see the screen shake and my health fall, and I'm thinking, "DRAGONS!", and then I turn and see one of my lovable giant buddies attacking. I didn't learn the full extent of their power until I was wondering around near Whiterun with my first playthrough and I chase a fox into a giant camp. Next thing I know I'm hearing battle music and flying up high enough to see the white-gold tower.