What fish should i get for my 125 litre tank ?

Okay ,i have a 4 inch red-tail black shark ,two ,3-4 inch austrailian rainbow fish ,1 small angelfish ,1 big angelfish ,two ,3 inch golden gourami's ,a 1 inch black phantom tetra and about five ,1 inch golden apple snails .What other fish can i get ,i want a big fish like a 6 inch-ier ,myabe a discus ,or a couple of small 3-4 puffer fish,any ideas ,i reaally want a fish with character ,please help ??