You said beginner fish, so it all depends on your interpretation.
If you mean for inititial cycling, then a hardy fish would be great. The same thing goes for the beginner. However, these fish might just be a "trial run" to make sure you don't make mistakes later on (cruel, isn't it). Many people decide to keep these fish because they are fun to watch and good community fish.
However, if you have a fully cycled tank and are just restricted to being a beginner, you have more choices.
Livebearers are good for these people, but then they have to deal with fry, which may be a bit out of their league.
However, going with livebearers of the same sex is a good idea.
Danios and the like are hardy fish that add excitement, but they aren't as attractive as other fish, IMO, and they may contrast with the other inhabitants.
So, in the end, it's up to you. The fish mentioned by everyone here are good to start off with (though I would stay away from neons and such until you have more experience). Choose a type you like and which you want to keep in the tank after the "test run."