Praets are the best, but any of the other very strong early rush units get votes from me:
Quechua, Immortal, Vulture (basically a swordsman that you can use in an axe rush)
My other 2 candidates would be Cataphract and Jannisary, 2 units that absolutely dominate everything else on the field at the time you can usually get them. For both of them, you can basically run through whatever they have, only using siege when facing a city with unusually high defenses or high defenses and on a hill. Very powerful for a later game rush.
Quechua, Immortal, Vulture (basically a swordsman that you can use in an axe rush)
My other 2 candidates would be Cataphract and Jannisary, 2 units that absolutely dominate everything else on the field at the time you can usually get them. For both of them, you can basically run through whatever they have, only using siege when facing a city with unusually high defenses or high defenses and on a hill. Very powerful for a later game rush.