"Worst" Unit

[Juvenal]

Like Sygrod, I have had a bad experience with catapults.

I thought I could use them in my KH elite army for administering the final solution to the Romani.

The first problem is that they are hideously expensive - especially in upkeep, so I delayed building them until the rest of the army was ready.

Secondly, they are very slow on the campaign map. I had to ship them from Athens. They took so long to sail to Italia that by the time they arrived the Romani core cities were already captured. So I sent them to my final objectives in Iberia (which took another couple of years of sailing time).

So finally they land near Arsé and manage to knock down the wooden gatehouse. This just left me with Emporion and Massalia to capture.

I made the mistake of sending them overland. Of course I got waylaid by the Lusotannan. Catapults are a liability on the battlefield. My entire army found itself acting as a catapult-guard while the catapults killed half a dozen Lusotannan, then several dozen of my own troops who got in the way (damn fire-at-will).

Because of the catapults, it took me another two turns to reach Emporion, by which time the Aedui had turned up and I got waylaid again.

I think I could have maintained 4 or 5 traditional Hoplite units for the cost of that single catapult. I don't think I will be building them again.

[Tellos Athenaios]

Like Sygrod, I have had a bad experience with catapults.

Catapults get my vote as well. Not because of the unit, but because this is the only vanilla unit left in EB. (I know it is (virtually) impossible to make new siege engines work in RTW, I know. But still...)

Catapults can do serious stuff:

1) In densely populated area's, such as Hellas they allow for some really fast conquest. Think of it: you Seleukids at war with KH, ship two armies to the southern part of the Peloponessos (one for assaults, one to use as multiple garrisons packed together), wait a turn when you've got their (use army 2 to screen army 1), attack Sparte and Korinthos all in the same turn. Next turn: hit Athens & Chalkis.
2) Hunting down: army attacks enemy forces, driving it towards your catapult army which then get to destroy the army completely.