The unique 100% automated thing I've ever built was in my 1.2.5 world, and now I'm porting it to my FTB world with some tweaks. Basically, a couple of tree farms and a wheat one are connected to 3 commercial steam engine. The wood from the tree farm get smelted by a TE furnace, the charcoal produced keeps the low pressure boiler (2x2x3) heated, generating some extra fuel after a little while. Wheat farm splits its outputs: seeds and around 1/4 of the wheat get autocrafted in plantballs that get macerated into dirt, then the remaining wheat and dirt get autocrafted in compost that goes to another crafting table to be converted in humus together with some more dirt from plantballs. The humus get routed into a chest that keep supplied both arboretum, the compost goes into a fermenter that produces biomass together with the extra saplings from the tree farms.
So, products of this contraption: biomass, charcoal (not that much at the beginnings, a load while the boiler gets heated), 100% automated.
The other factories I've built were EE2 condensers based, so no real automation. Thanks god, now EE3 removed those infernal devices and I can start using my brain knowing that maybe there's not a way easier and cheaper way to achieve automation.