I will mention other concerns in parentheses, as they may be useful later.
The wiki article on weapons has something to say about this. For unarmored squishy types bladed weapons are best, and for armored squishy types piercing weapons are best because slashing weapons have significantly reduced effectiveness.
What it doesn't mention is that piercing weapons are still quite effective against unarmored foes. So when I don't know if an enemy will be armored I would go with spears (well I usually go with crossbows, but that's for defensive reasons). Spears are better weapons than picks (Though your dwarves who use picks are often more skilled with them.), and all other piercing weapons are foreign (I suppose that is not a consideration with fastest kill, but I don't have much experience with them).
However, my own experiments in the Object testing arena show that even in heavily armored fights battle axes beat spears nearly every time. Testing of swords vs. battle axes also gave battle axes the victory.
Do note that if you are fighting Necromancers, as your newest list indicates, slashing weapons are a very bad thing, because you will also be fighting zombies, and a zombie with an arm cut off is much like two zombies. All your other entries are lightly armored, and thus slashing is most effective against them.
That's about as much as I can say about organic enemies in general. If you want to test against a specific enemy setup you can use the object testing arena.