> I have only used UUID and postgis.

If you used "uuid-ossp" to get uuid_generate_v4(), then this is no longer necessary since Postgres 13 as there is now a built-in gen_random_uuid()

https://www.postgresql.org/docs/current/functions-uuid.html

The ltree extension is fantastic if you have data like comments or any other hierarchical structure.

Well, I wouldn't call it interesting, but I like the citext extension for case insensitive comparison.

TimescaleDB

aws_s3: https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_...

pg_stat_statements