While most of these have been mentioned before, most are in other sub-genres such as magic and explosives and the like, and according to search I think a topic that would bring them together would be alright. I will probably be proved wrong.
With the new system creating so many zombies and bandits in droves who would chase you down causing much fun, being able to do something to injure multiple targets would really be quite useful and a change up from running away to throw daggers at them. All ideas are welcome, but with toady wanting to keep it to 1400's technology, keep it aimed towards that. Ideas from other topics would also be good, so it can be placed into one space.
Suggestions:
Molotov / Oil and wick: Being able to throw oil which creates fire would be alot of fun when being chased by zombies. Walking into a tower then throwing it on the ground to watch as stupid zombies wade through it and catch on fire to get you would be really rewarding. I know that modding in flame attacks similar to a dragon can give you the same sort of ability, but being able to do this with items would be pretty fun.
Magic: Everyones heard of it so I wont explain it, but it will definitely have some system when implemented.
Sweeping weapon attacks: Probably restricted to 2 handed and larger weapons, being able to hit multiple opponents in the same spot or who are next to each other would be nice. It doesnt have to hit every person around, but it makes sense that if 30 people are on one tile, more than one of them will be hit with a 2-handed sword swing.
Impale through: If a dwarf with superdwarven strength throws a spear at someone, maybe it might pass through and injure the person behind them. I hardly think a kestral would stop a spear thrown at point blank range from Urist McHulk
Powders / poisons: Grind a few poisonous plants and make it into powder form, throw it at some enemies and watch them retch. Only work on the living, and doesnt have to be overly powerful. Maybe through some flour, then add fire and BAM, explosion.
Smokebomb: Could reduce visibility to one tile around for all caught in the smoke. Good way to escape, restict attacks to those close to you or take advantage of.
I think I can say that everyone likes the idea of making a character that is unique in a way, and above does offer some berserker, assasin, ninja type abilities which helps to make your playthrough nice and special.