Hum, I have to disagree with most of you, since I dont think any unit is useless.
There are some very weak units like the pantodapoi, but I can always give some use to them, using them to distract enemy phalanxs to attack them from the back with cavalary (even skirmisher cavalry are good enought to this job) or shock troops.

And with the elephants or the scythe chariots I have to fully disagree since they are an battle winning force , you just need to use them right and carefully.

And the toxotai, they helped me an lot at the start of my epirus campain, helping me to have greater numbers with small costs while facing the lots of mak stacks and they worked very well.