Replacement materials for boat parts

I recently replaced a few small parts on my Hobie catamaran and found that fiberglass works surprisingly well for them. Thought I'd share with fellow boat owners.

The plastic fin guard at the stern had a small crack after scraping against reefs a few times. Later, I had a craftsman make a fiberglass replacement. It's slightly thinner than the original but has good hardness. Last week, I scraped it again in shallow water and there wasn't even a mark left. Plus, this material isn't afraid of water exposure. The old plastic one always swelled a bit around the edges after long use, but this fiberglass one still looks neat after cleaning.

There's also the foot brace on the deck. The original metal one started to rust after two years. After replacing it with a fiberglass part, it's much lighter, saving me some effort when lifting the boat each time. I don't even need to dry it specially after being splashed with seawater.

It seems fiberglass is really suitable for such small parts that are often in contact with water and occasionally get bumped. I wonder if you have similar vulnerable parts on your boats? What materials do you use for replacements?