I agree with the above but if you go for platies be careful as if they breed they'll rapidly over-stock the tank while it's still cycling. Also, danios should be in at elast a 20 gallon and in a group of 5 so keep that in mind. Black widow tetras need to be in a group of 6 so do keep them in an adequately sized tank. Basicaly, go for platies for a small tank and either of the others for a larger one.
You may also want to fishless cycle which is quicker and less stressful for both you and the fish and provides more margin for error. Read the link in my signature for more information. BTW, you don't need to use pure ammonia, fish food would work too.
I am also curious as to whether anyone has tried purposefuly cycling with snails? They produce a lot of waste and I do know of instances where they cycled the tank but it was not the owner's intention so I have no idea of how long it took or similar details. I think using snails to cycle a tank might be ideal in some situations...