You want a full list of every possible summonable creature in the game? That's a bit of a tall order...especially if you want to know what each one does! I'll tell you what, though. I'll get you started with the entire Met archive.summon DozerMetool//Summons a Metool that runs around.
May drop Quick Boomerang or Item-1.
Does collision damage.
summon ChaseMet //Summons a Met that chases nearby players/bots.
Fires shots and does collision damage.
summon LazyMet //Summons a Met that pops up, fires a shot,
and settles back down.
summon FranticMet //Summons a Met that does nothing but chase nearby
players, never firing and never settling back down.
Does collision damage.
summon JumpingMet //Summons a Met that jumps and fires a shot
before setting back down.
summon MetDance //Summons a Met that's SUPPOSED to twirl, but instead
stands on its toes and fires five shots.
Replace "summon" with "summonfriend" to make the enemies your allies.
Their kills count as your own!