I think the battle droids were a cool idea.
As much as it pains me to bring up TPM, I've gotta say, one of the most interesting things about the world it presents, to me, is the battle droids. Sure, we can joke about how easily any one droid can be taken down by a Jedi, how clumsy and stupid they are, but in large numbers... oh man. These battle droids are TERRIFYING. Like, as a concept.
Remember, this was a few years before the Galactic Civil War broke out and you had these being deployed everywhere, and before the clone army came along, so whoever was making these droids back then basically pioneered the concept of a made-2-order army. Sure, there have been droids built to fight for thousands of years, aiding the Sith and the like, but never in such large, efficiently distributed quantities. It's like ordering a coupla' hundred pizzas.
Say you're some rich jerkwad, like a Hutt who's had enough and wants to kill off his enemies overnight. No problem! Just ring up these trade guys and they'll send you an entire platoon for cheap