What size tank are we talking about.....there are alot of good beginner fish (most mentioned above), but you can't put them all in a small tank.
Knowing your tanksize, we can better help you plan out your aquarium (if you want some help). 
Tetras, danios, guppies, platies, cories, plecos (Bristlenose and Rubbernose are good beginner plecos for tanks 20g and up), loaches (yoyo, polka dot, kuhli, and zebra to name a few....all but kuhlis need atleast a 29g IMO...kuhlis are ok in a 20g), bolivian rams are ok for beginners.


Tetras, danios, guppies, platies, cories, plecos (Bristlenose and Rubbernose are good beginner plecos for tanks 20g and up), loaches (yoyo, polka dot, kuhli, and zebra to name a few....all but kuhlis need atleast a 29g IMO...kuhlis are ok in a 20g), bolivian rams are ok for beginners.