In addition to the "normal" birds, squirrels, mailmen and cats, I've seen huge red-headed woodpeckers, swarms of prehistoric jumbo-sized dragonflies, cardinal families, and other assorted creatures from the comfort of my office.
The other night, I heard a hooting out back, and saw the most enormous owl I'd ever seen. It had to be 20-25 lbs (that's over 9 kg for those of the metric persuasion!). Paul brought out his binoculars, and even Zack came out to look. The feathers were so fine they looked like fur.
This morning, I met a frog. I called him Jack. I met him out back. Max didn't attack.
Lucky frog :)