I don't know what they are named, but...

Sewer Hydra
  Hope you brought a pistol or plasma rifle. Although the Rivet Gun will work, it is
difficult. Then... telling you to freeze the fan just seems like going too far... as I
just did.

Stone Gorilla
  Freeze it right before it gets to you.  Then shoot it's hump back.
  TK (grav catch) the slime it shoots at you, and shoot it back. Shooting the slime balls
so they explode in its face didn't seem to work.

Space Hydra
  (Not that you need these specific weapons, but they worked pretty well.)
  Plasma Rifle primary the pads under the claw arms.
  Arc Weld primary the pollups in it's mouth. The Rivet Gun primary works, but is
difficult.
  Line Gun a timed mine onto it's balls, and follow up with a line gun shot and Plasma
rifle primary to finish them off. Aim for the ball closest to it's body to save ammo.
  Rivet Gun secondary into its face/eye thing.
  ...After cutting it's balls off multiple times, it won't have as many to smack you with
(or for you to blow up). I'm not sure hitting it in the eye does much of anything.