Eagle Warrior (Aztec) - 13
Hetairoi (Macedon/Alexander) - 17
Mamluk (Arabia) - 5 (8 - 3) Great unit, but arrives much later than the other remaining units. The other units will help you out much earlier, thus having a greater impact on the game.
Pítati Archer (Nubia) - 40 (39 + 1) Simply the best UU in the game. Archers are already great. These have great mobility combined with range, which is a huge advantage, even before you consider the additional strength and synergy with Nubia's UA (which I feel is fair to take into consideration, as it is clearly designed to benefit the Pitati Archer).
War Cart (Sumer) – 33
The changes in the Spring Patch are interesting. The change to Commando is a decent boost to all Melee units, which mitigates one of their most significant drawbacks. You do have to get to the second tier promotions to get it though, meaning this is a bigger boost to the melee units which can be upgraded into, or in the case of the Eagle Warrior, are available from the start, than the ones which must be hard built later.
Additionally, the Spring Patch buffs some specific Melee units, which would probably have done better in this thread if the changes had been taken into consideration. Apart from possibly the Immortal (which was apparently bugged) these are still nowhere near top tier, though, as they have to be hard built. That said, I find the Berserker changes to be particularly: With the Spring Patch, these are now potentially faster than Knights (in enemy territory), cheaper, and can hit harder. In addition to this, they pillage faster, and can embark and disembark at no extra movement cost. This makes them much closer to what I believe they are supposed to be thematically: hard hitting, mobile terrors on the coast. Consider a berserker with two promotions, Battlecry and Commando. On the offence, this unit has 5 movement points, embarks and disembarks with no additional movement cost, needs one less movement point to pillage, and hits for a whopping 57, more than the base strength of a Musketman. The only thing the Berserker lacks to be really good now, is the ability to upgrade into it.