Greater Deathblow!(Userunfriendly)
Well, if I am writing this guide, you knew I would include this....this is my favorite cheese, and I invented it...once you get the high level ability greater deathblow, equipp an area effect weapon, and activate the ability and fire the area effect weapon into a room full of annoying fodder, like mind flayers and beholders, and every monster in the area of effect will die, dropping like poisoned roaches. You see, most of the "fodder" creatures in the game, are below level 12. And greater deathblow completely ignores saves and magic resistance, if a creature is below level 12, being hit with any weapon while greater deathblow is active will insta kill them, no saves, no resistance, only deathward will protect them (darned drow priestesses!!!). Area effect weapons like fire seeds, courtesy of any druids, like Jahiera or Cernd...also arrows of detonation works great, so does the frag grenade ammo used with the big metal rod...
Tips
Area effect nastiness includes the most useful ability, greater deathblow, but also includes smite, (blow all nearby enemies away from you like the wing buffect dragon ability) and power attack (a fighter version of power word stun, this is particularly nasty if you are using energy blades, you can stun almost anything with a volley of power attack energy blades) and poison weapon (poison a room full of goblins in one attack) and even if you dont have area effect weapons, its pretty awesome...try it with melf minute meteors or energy blades if you are a fighter mage, or have sola for quickly killing most of the enemies in a room fast....this ability kills mind flayers, beholders, trolls, vampires, umber hulks, drow, and some demons(tenari)...but certain individuals of these types are immune, since they are above level 12(does not work on named vampires, for example, and mindflayer liches, in the mindflayer lair in the underdark, and elder orbs or hive mothers...)....and vampires can be killed with greater deathblow, but you cannot hit them with +1 weapons, like frag grenade or arrows of detonation...use melf or energy blades to kill vampires fast...the usual rank and file fodder creatures that makes many "boss" encounters difficult can be slaughtered by this exploit, thus you can kill off the "support" enemies and concentrate your party attacks on the boss...who is feeling pretty lonely once its support creatures are dead.