Orange Diamond Goby Valenciennea puellaris 
Reef Safe: Yes.
Attitude: Peaceful.
Diet: Likes meaty foods. Formula 1 is a big hit. Mysis shrimp.
Care: Easy. The bigger the sand bed the better.
Origin: Sri Lanka.
Personal Observations: These fish were the missing piece of the puzzle in my aquariums. In my old tank and now this one, I had great looking corals and fish, but the sand always had a couple spots with cyano on it no matter what I did. Not anymore,
THESE GOBIES ARE MAJOR SAND SIFTERS! As you can see from the pics below (click to enlarge), my sand is back to being pearly white thanks to these guys. 
Look at what they are doing to the hard sand in this photo. 
Initially they really stirred things up and debris was flying for a few days. This really stressed me out and I wondered if I made the right decision. I don't wonder anymore. After they made their burrow and got rid of most of the fine debris, things really settled down and my sand looks fantastic. No more algae on it anywhere.
These fish have a lot of character and it's cool to watch them sift sand through their gills. They are peaceful and not skittish of other fish or even people. I was lucky to find a pair as they cruise around together and mimic each others moves. Once I saw them dancing around in a circle. Maybe they will mate.
Why do some discourage buying these?
Some shun these fish because they fear they will eat all their bugs in the sand. Well I never was big on the creepy crawly stuff and I still see tons of pods in the tank on the rocks and such so I don't worry about it. Personally I would rather have these cool fish and perfectly clean sand than bristle worms, etc. Note: They do spit out my snails unharmed. Not sure what they would do with worms.
Feeding:
Yes! Unless you have a huge tank with a mature large sandbed, I would say definitely. They will probably starve otherwise. My tank is not large so I make sure to feed enough that I see them getting some. Initially I buried some food near their burrow and they would dig it out. Now they go right for the food when they smell it in the water so I don't have to do that anymore. Formula 1 is their favorite. They eat mysis shrimp too.
Warning
These fish can be jumpers. I haven't noticed that behavior with the ones I have now, but the one in my old tank definitely was. Take precautions with either a glass top or some egg-crate. At least a lip a couple inches out from the sides would be good.