I'd echo the fourth post here and suggest that you pick something you have a real interest in and also something you are knowledgeable on. If you aim to concisely and persuasively present your knowledge on a topic you know a lot about, you have a good chance at writing a very good essay.
You will almost always have a series of choices, or one topic. If it is freewriting, you might want to write about something that has personal meaning to you. Consider a life experience that you can write a personal narrative about, for example.
I agree with the second post. Of course, it's important to remember to write correctly on whatever topic you choose. In other words, grammar, sentence structure, punctuation, and other such matters are all crucial, no matter what the topic of the essay is. Poor grammar can hurt the reception of your writing even if the "content" is interesting. If your grammar is consistently very poor, people will assume that you don't read much and are therefore uninformed. Here, by the way, is one of the very best sites on the Internet for help with grammar and mechanics:
I don't know what your choices are if they are delineated for you, but I know that you will write the best essay on the topic that matters most to you. You will have stronger and more personal examples to develop as evidence of your thesis, and the essay will likely reveal something of your voice as a writer. Don't try to guess which topic the evaluator will like -- you don't know the evaluator. Write the essay that means something to you personally.