I agree about jags being weak, and they're the only ones of those I've used, but I can't see the samurai being useless since it's an improved maceman, the musketeer being useless (although I rarely bother with musketmen) since it's a very early mobile infantry, or the phalanx being useless since the horse archer period is pretty long (and the AI at least loves to use them) and elephants are annoying.
