I'm interested to hear about effective Puerto Rico tactics that people don't see very often. Here's one I have in mind:

Some characters can be chosen a second time in a row to potentially devastating effect:

Craftsman: you produce first, barrels run out on other players.

Captain: you ship your entire crop from your warehouse, other players ship single barrels or nothing.

Builder: You build something you want with a few leftover gold, other players pass because they haven't gotten income yet. (Also, you can plan ahead for this on the prior builder phase, others can't.)

Trader: No-one needs gold other than you / no-one has barrels to trade other than you.

The downside is there's never a free gold for going this route, but I expect it's worth it more often than people realize.