here is a list of dariusrulez's mob ideas (me)
vampire:burns in light,causes bleeding.
harpy:spawns above clouds,drops harpy feathers
red:sets player on fire,drops blaze powder
blue:shoots bubbles that can drown players.
green:shoots seeds,gives random sapling.
purple:uses poison gas.
cyan:most common,drops wisp dust
yellow:very weak,in groups
frankenstein:stronger zombie,drops bolts
hellhound:nether version of wolfs,hostile from start.
bogma: kelp creature that spawns in swamps,drops moss.
yeti:spawns in snowy biomes,strong
mummy:desert version of zombie,weaker
ghost:spawns when a player dies,can only be hurt with weapons that have the "spectral" enchantment
poltergeist:it looks like a faded grey head that spawns in abandonded areas,attacks with blocks
nymph:spawns in strongholds,plants saplings
wyvern:spawns in wyvern lairs,weaker ender dragons
triffid: a walking plant that hungers for flesh,can cause hunger effect and poison
hornet:very annoying,in groups
alien:very rare,drops raygun
minotaur:spawns in nether or a cow that gets struck by lightning,drops battleaxe
boar:brown.stronger versions of pigs,netural,drops boar chops
zombie boarman: spawns when lightning hits a boar or spawns in the nether,stronger than zombie pigman.
demon:spawns in the nether,can fly
zapf: a monster made of riches badly damages swords when fighting,drops a lot of gold!
pegasus:winged horse,drops pegasus feathers
meenlock:lives in caves,strong
ceberaus:very strong bite,spawns hostile wolfs
chinese dragon:very long,fire is deadly
queen bee:spawns in gigant beehives,summons bee minions
test subject 11: a cruel test gone wrong,spawns in nether labs
new jearsey devil:rarly spawns in forests,can fly
displacer: can attack you with its tentacles,rare
ezerhorden:a lot of heath,only "spectral" enchanted weapons can harm it.