So, let's compare the remaining units.
Camel archer (7) - Replaces the Knight. They have 3 less strength but can do the move forward, shoot, and retreat bit, with more effect and
more strength then the DLC
Keshiks.
(Keshiks have 5 move, but weaker RA) [...] because when they upgrade to Cavalry, half of their promotions become useless. I predict they are next to cut.
- NEVER upgrade them to Cavalry and you're good until Tanks! Blitz +range = unit slaughter when in packs. Cities as well after siege, given it's about HP not strength.
Mandekalu Cavalry (31) - Same strength as the Knight, but they get a massive
+8%?? bonus against cities instead of a -25% cut. Chivalry is harder to RA block then Steel, but more useful too.
(3 RAs gets you to Chivalry by turn 70) This basically makes them like the Knights of old...
(random aside, Education is beside Chivalry - not needed or connected to it, Economics is 2 techs above Chivalry) The two you might be looking for are Civil Service and Currency
Combined with the Songhai bonus for pillaging cities, you'll want to build a large Mandekalu army, and then rush down cities like no tommorow. I predict 4th.
Cossack 11 - Hmm. Cossacks get a bonus against wounded units. Can't say much about them b/c I haven't played with them significantly, but their UA doesn't seem like such a deal breaker in a pitched battle. Still, they must be monstrous at cleanup and sniping the wounded. I predict second-to-next to cut.
Immortal 20 - Get 2 heal in outside territory, 4 in friendly,
6 in a city - all before march/medic - which means that, as long as they're not facing down a teched-
up or walled-out capital, they can camp down cities and shug off whatever the enemy throws down.
An aggressive unit early game, and great for defending against over-militaristic AIs, esp. on Diety. Also have 1 more strength. I predict 8th.
(plus, who doesn't like 10 Immortals upgrade to Rifles?)
Legion 20 - Get 2 more damage and can build roads. Classical rush with 5 Legions. Like Swordsmen but better basically.
(which isn't actually saying anything when the above mentioned Immortals can chew through them during a GA) I predict
12th due to nothing useful upgrading to LSs.
Foreign Legion 25 - Aggressive
Infantry with a bonus on enemy territory. War war war, basically. Imperialism ftw!
Never obsoletes, so you can build these and upgrade to mech infantry to keep the promotion. I predict 6th.
Longbowman 24 - Get 1 more range. Helpful for sniping units down, defending your territory. Insures they won't get run over by Knights without having their fair share.
(one shot wonder if against a knight with a clear shot) I predict 7th.
Naresuan elephant 28 - Super heavy Siege engines. I remember MadDjinn pointing out somewhere that it was mathematically pointless to upgrade them to Cavalry.

They have one less move but 4 more attack then Knights, AND get a
50% bonus against other mounted units. Almost break even with Pikes, actually. I predict 3rd.
Chu-Ko-Nu 36 - Double fire Crossbows that can thus actually attack cities with some affect, but are
just as frail to direct attack. Also good at finishing critically wounded units. Build a whole bunch of them and enslave the world. Biggest con is the fact that their promotion path goes through the Ranged promos, which, once upgraded, are useless.
- except the 2X attack promotion sticks. So a mass build/upgrade to rifle strategy gets 2X attack rifles without promotions. I predict 5th.
Samurai 34 - Get Great Generals at
faster speed, also start with Shock I. With an Armory, that means you can get STARTING Samuri with Shock I, Shock II, and Shock III right out of the gate. The jump to 60 experience isn't so bad, another 6 battles I think, but jumping all the way to 100 is hard, something like 8 battles on top of that. That basically means that Samurai get March/Blitz a faster then regular Long-swords. Plus, they are in that critical area when you just have enough resources to start uber-warmongering. Plus, they form the backbone of your army for the rest of your game. Plus the Japanese UA pumps them up even more. Methinks, 2nd.
Janissary 40 - They heal fully when they chew down on another unit.
They also get a +25% attack bonus. They would be overpowered, 'xcept for the fact that the rest of the Ottomans is totally worthless

Jannies can smash through attacks again and again, without having to heal. The tradeoff is of course the fact that you have to hard-build them, because those pesky Musketmen don't upgrade from anything. Shucks. Obviously 1st.