Here's a short list of fish/inverts that do a "job" Remember that most of these creatures only help mitigate problems and the things the help solve should be taken care of at their root.
Algae Control:
Rabbit fish
Foxface
Sailfin Blenny
Mollys (yes the 'freshwater' kind)
Sea Hares
Emerald crabs (hit or miss with bubble algae, may nip coral)
Various Snails
Pest Control:
Cleaner Shrimp (I love mine, weather he does anything or not, I don't care, he is very cool and active.)
Various Nudibranchs (remember there are far more dangerous kinds then good)
Copperband Butterflies (aptasia and other pest anemones)
Thats all I got for now.