One of the little touches that made Diablo 2 really sing, in my opinion, was the useable quest items.

It's one thing to pick up a greentexted item and make inventory space for it, it's another level of interactivity with the world and the story if you're able to pick it up and USE it.

Starting as early as Act 1, you're able to to find and use "Wirt's Leg." It's a pretty crap weapon, but, hell, you're swinging a dude's leg around. In Act 2, you get Staff of Kings, the Amulet of the Viper and THEN the Horadric Staff. In Act 3, even more.

Now, they're usually consumed/transmuted into something else, but at least you can use and interact with them for a while.

I remember with prefect clarity realizing I could USE the Horadric Staff, and that it out DPS'd my current weapon.

I would LOVE to be able to wield Milagro's Spike, or socket the Baleful Gem, if only for a while.