If I could choose anythind and ignore tank sizes and compatibility etc (oh and my ability to be a good mother too!)..
Jack Dempseys
Oscars
FW Stingrays
FW puffers
Blue Lobster (not really a fish - I know!)
Killifish
Clown loaches by the gazillion
Neon Tetras
Kribensis
A fish I have no idea of the name of - but it had the beautiful colouring and markings of a leopard - and was large - about 6", I've never seen it since! (helpful!)
And in the real world I've chosen (so I like!)
Neon tetras
Guppies
red tail shark
Clown Loaches
Kribenses
Angels
rummy nose tetras
dwarf guarami
zebra danios
armoured shrimp/african dwarf frogs