I think Bettas in my personal opinion (so far), everytime i go close to the tank, my Betta, Firefly comes closer... and starts 'showing off' and he hand feeds.. lol, he also gets along well with the neon tetras, there's the occasionsl chase now and again, but nothing bad!
#1 I think there are a lot of really friendly fish...otherwise we couldn't have community tanks I guess. If I had to pick I guess I'd go with a type of rainbowfish or peaceful tetra like white skirts or blue tetras. Out of the fish I own I think it'd be the blue tetras for most sociable and nice to other fish in the tank.
#2 Oscars are definitely known for their human contact...so much there are even stories about people petting them and what not. I'd say #2 is between Oscars and bettas.
Friendly to other fish: Livebearese (ie: guppys, platys, mollies)
Friendly to use: Bettas, I had one once that I trained the "dance", using the magical bloodworm.
Half-beaks are also ver friendly, mine come right up to the front of the tank to beg for daphnia.
My angelfish will hand-feed, always come to "see me" and wiggle when I walk by the tank. Funny thing is though, they aren't as friendly to my husband (he rarely feeds them). I personally haven't had a problem with angels being aggressive to other fish, but I've also never had a breeding pair, either.
My rainbowfish are new, but seem friendly already.
id have to go with the platys mollys guppies, or even the little albino corycats on #1 and n #2 the oscars, if you talk to the bigtime oscar fans, they train their oscars to do tricks like jumping thru hoops and doing certain routines for food, letting you pet them, like an underwater puppy. they'll even play with a pingpong ball if you sink it in the tank.
I had oscars before that would follow you if you walked in front of the tank, eat out of your hand and look over your shoulder when reading a book. He would also puff out his gills charge at the glass if the cat got to close to the glass then the cat would go running out of the room.
Platys,cories guppies are all friendly fish. My mom has Oscars and they are very social... my orandas and bubble eye hand feed and race to the glass front to greet me when i come home from work. So do my angel fish.
All of my fish (with the exception of the plecos) come running to the front of the tank when they see me or my cats and they all eat from my hand. I have angels, platys, mollies, rasboras, corys. My betta that I keep at work is very social. He will come to the front of the tank and wiggle constantly when someone is at my desk.
Cichlid only tanks can provide what a community tank does too! A cichlid Community. The aggression is balanced (if stocked right) and everyone gets along with everybody for the most part.
I say Cichlids for both, however the South American/Central American species tend to be more sociable towards us as people than do the africans.