What should I do for a Halloween costume?

I am trying to figure our what I want to be for Halloween like half Jekyll and Hyde or Pirate and Mermaid etc, should I do a half n half costume or something different? I am a 25 year old Male, slightly out of shape, but not terrible. Anyways, please suggest some ideas and I will use them for my costume! I am wanting to do something that pushes the limit and will get attention and push my comfort levels. Halloween is almost a challenge to myself to try something new and have fun. Thanks for the advice in advance!