sendos
Immortal
Do you know off-hand if Immortals keep that promotion upon upgrade? Been forever since I've played Persia and honestly cannot remember at all. If so, that is a solid unit for the entire first half of the game.
In addition to this question, has anyone ever been Persia and had the Fountain of Youth nearby? Does it provide +40HP healing for immortals?
African Forest Elephant 7
B17 22
Battering Ram 20
Berber Cavalry 21
Berserker 7
Camel Archer 32
Carolean 34
Chu-Ko-Nu 34
Companion Cavalry 16
Conquistador 19
Cossack 25
Horse Archer 22
Hussar 22
Hwacha 24
Immortal 18
Impi 28
Jaguar 24
Janissary 27
Keshik 35
Legion 21
Longbowman 36
Minutemen 20 Upgrades carry on to later troops. Free drill promotion + military buildings (+ Brandenburg or Autocracy level 2 tenet) enable getting the elite promotions very soon. Having a mech infantry with these upgrades is quite awesome.
Mohawk Warrior 18
Musketeer 2 Strength upgrade is so short-term. It might encourage France to zerg in the Renaissance era but if you're behind in tech, that doesn't matter much.
Naresuan's Elephant 24
Pathfinder 32
Pictish Warrior 16
Sea Beggar 27
Ship of the Line 31
Siege Tower 33
Tercio 21
Winged Hussar 26
thanks for that information though. At least I will know in advance if such an opportunity appears. 
There are some interesting things to do with some UUs. Today, I got Landsknechts from the Commerce policy tree, as Poland. They became W. Hussars with free pillaging (!!!) and double gold from city capture. So, it had 5 movement, 28 strenght, Shock I, Heavy Charge, Shock II and III (because of Barracks + Ducal Stable), Formation, Free Pillaging and Double
from city captures. Some of the best units I've ever had.