Ok, the coolest part about Titan Quest is the rag doll physics. They are hilarious. Special attacks cause bodies to fly way up high in the air and come down in all sorts of odd places.
The variety of character classes is neat too, although I feel a bit trapped by my current build. I started out as a hunter, which means spears and bows are my weapons, and then combo-ed in the warrior. So I'm pretty badass with a spear, but I rarely use the bow. I'd like to try a few different builds, but I don't want to hack my way through the levels again.
I'm almost done with Greece, which is the first of the 3 parts. I haven't tried online yet.