Voice acting + microphone + EQ = good monster effects to me in a nutshell. When using a dynamic microphone you can just get the raw directional sound of a voice usually for growls or moans etc. But when making a gurgle sound to capture the embellsihments of someones voice I usually use a condeser or a ribbon microphone. If doing a monster I usually record my self at a high sample rate therefor I can transpose down to make it sound less me and more inhuman and then I eq it to roll the highs or the lows off. Some times I will duplicate the track and add a second affect and turn the volume down alittle to give the voice alittle extra feeling. Maybe I should make a tut on this.

"Maybe I should make a tut on this." Please do. =) I've always struggled to record decent monster sound effects.

Well, I mean I could but the way to make monster sound effects is pretty subjective. I mean I guess I could show how to make very primitive monster sound effects. I mean you can go outside and record a ac unit by your house and manipulate that to make a weird monster. Usually recording your voice and only chaning it alittle to make it sound less like you is the best bet you have and then bring out which frequency you want more, Low or highs.