This depends so much on the definition of 'best'. For what it's worth, here's my view from the perspective of a chemist.
Easiest - Shipwrecks - note that this doesn't mean you'll get the best marks, because there's a lot of competition, but this is definitely the easiest in conceptual terms.
Chemically most useful - Industrial. If you're going on with chemistry, then the quantitative treatment of equilibrium that is in this elective is something you want to have seen before. I would consider the redox in Shipwrecks as a distant second here - it would be closer, but the syllabus makes such a hash of dealing with the important chemistry, that it ends up a distant second.
Most 'interesting' - most people like the fact that forensics seems relevant (in a societal sense), but I think you really need more background to really appreciate forensics - chemistry of carbohydrates and DNA need so much more than you have at this point to be really understood.
Most dangerous - Chemistry of Art. This has some really nice inorganic and transition metal chemistry in it, but I have serious doubts that there are many teachers actually qualified to teach it. The chemistry here is best left to Uni, IMO.
