One of my personal all time favorites is the Six Line Wrasse. It eats flatworms, smaller bristle worms, pyrmad(spelling) snails that attach clams, etc.
Algea
There are many tangs available that stay smaller that will help eat hair algea and add great color (I have a Yellow and Regal).
Lawnmower Blenny(Algea or Sailfin, people call them lots of different things).
For Ich:
Cleaner Wrasse
Cleaner Shrimp
Cleaner Gobies (Neon Blue, etc)
There are also other fish depending on what your trying to control, example I have dragon faced pipefish for controlling SPS pests.
Hope this helps or atleast gets you started.