Watches

...it is never said that watches are a good investment, because they are a poor investment.

Watch values fluctuate like cars - the moment they leave the manufacturer/authorized dealer in your possession, they depreciate. Some watches do retain value better than others, but very very few ever gain value. Even nearly all vintage watches (i.e. those more than 55 years old and produced by a reputable company at the time), when accounting for inflation, will be found to have substantially depreciated from their original purchase price.

Watches with a high quantity of precious metals (e.g. gold, platinum) and gemstones will tend to retain their value better than watches of the same model/line that are made in steel or something less valuable and without gemstones, but they are also quite a bit more expensive (higher upfront cost) than their same-model counterparts.