[Iraf]

agreed, skunk cleaners are very sociable and they'll even jump on your hand and try to clean it when your working on things, their a opportunistic scavenger and will eat leftover food or catch mysis and things like that at feeding time, they'll also graze on seaweed or veggies you use to feed tangs

fire shrimp (the bright red ones) serve basically the same purpose but a slightly larger appetite as they'll go after some different worms in the tank as well that can be harmful so definetly a cool thing to have, not nearly as sociable though.

coral banded shrimp are territorial and can/will attack anything that gets close to them just cause they seem like their always ticked off little mutant 1/2 shrimp 1/2 crab freaks

Linkias are hard to keep, I have a friend thats had one for 18 months in his 210g but the tank is around 5yrs old and has it where even the water changes are completley automated on it.
Personally I have red thorny starfish in several tanks and they do great, very hardy and great scavengers, haven't seen them touch any corals or anenomes in any of the tanks