Squelch
Right click the link to the sample below, choose "Save target as ..." and save it with your other sounds.
Has your character ever got wet? Chances are they have. Sweat, rain, inadvisable swimming, all these things make your character wet. When wet, a character will squelch occaisionally until they are dry. Since squelching is a sound it makes sense for it to trigger a sound effect.
Follow the same pattern as door sounds to set this up (you have done the tutorial haven't you?) or cut and paste one of your existing door sound triggers and just modify the trigger and the sample.