When a sentence ends with な

There are two common ways a Japanese sentence can end with な. The first one expresses the speaker's emotion, wish and so on, and the な does not really translate into anything. In this case, we can remove the な and the meaning of the sentence remains the same, although it may sound like emotionless.

Examples:
東京に行きたいな = I wish I can go to Tokyo.
(The な expresses the speaker's wish)

それは間違っていると思うな = I think that is wrong.
(Here, the な emphasize that this is just the speaker's opinion)

すごいな = That is so great.
(I don't know how to explain the な here, it is just a casual remark)

The second common way な ends a sentence is when a negative order is given. The grammar rule "root verb + な" means "do not do something".

Examples:
笑うな = do not laugh
止めるな = do not give up

This seems to be used only by men, and usually is given from a man of higher status to a lower one (boss to subordinate, father to son etc).

Examples:
そんなことをするな！= Do not do that!