I've heard a lot of hate for Pacal and the Maya. Mostly saying their UU and UA are worthless. I wouldn't say they're the strongest, but I had no idea that the shrine replacement (pyramids) was so powerful. For the same maintenance cost and just a little more production I can get 2 faith AND 2 science immediately on a new city. And you can rush buy it for only 250. I was just playing them because I hadn't before and accidentally discovered that they can be a sleeper tech civilization. Ridiculously easy to get a good religion with them too due to the +2 faith on pyramids. I got the 2nd faith on deity with pretty much no extra bonuses and was riding the extra gold, happiness, culture, and faith ever since. I thought they were only a faith civ but I was wrong.
Originally I thought their little javelin guys were stupid, but then I realized how cheap they are--cheaper than archers. Most cities can crank them out in 1-2 turns and then it's only 100 gold to get a full-fledged bowman. Much more desirable than hard-building them, which is nice because it's the main defense and offense unit through a lot of early game. Pleasantly surprised by these guys.
Their UA isn't bad either, got a ton of free great people from rushing theology in the early BC's, but I did not realize you couldn't repeat units. I don't care about many of the greats, only a few in the beginning so the ability is kinda limited. Gave me a free wonder, early religious expansion, and tech though, so there's that. Could be critical if you play it right.