I just stumbled across this thread, and wonder what the best conductive filament option is now in 2018.
I've been using Proto-pasta's Conductive PLA to embed capacitive touch sensors in a project of mine, and it does work well for that purpose. However, it also tends to leave a mess of black "splatter" over other parts of the model. Not sure what's causing this, but its not oozing. Perhaps graphite powder leaking out during rapid print head movement? Really no idea, but its annoying.
I'd love to find other options to try, but its hard to track down what the good ones even are. I've seen BlackMagic3D mentioned in some places, but their stuff is hard to find and I've only seen a few resellers even admit that they have a 3mm option.