How to make a spike which isn't this aliased

#1 Render at twice the resolution in maya (Render settings) and shrink it down in photoshop/gimp.

Photoshop actually has a type of filtering for reducing image size to create a lot of fidelity

EDIT - That's the simple way. The more advanced way is to mess with your render settings. In general, a quick way to get better results is to change your render preset to "Production Quality" instead of preview. This will automatically bump up your filtering/aliasing/overall lighting quality.

#2 Are we talking 2D or 3D here, Ian?

#3 Ah, I was assuming 2d...

If it's 3d, there's probably and FX setting in the engine somewhere. You should only need a 6 sided tube to get a smooth shape on something that small.

#4 Torque by default has antialiasing set to 0 (except T3D beta 3 which had anti aliasing set to 60... that was slow, but boy was it smooth :p)

Anti aliasing of 3d can be controlled by the internal settings or you can create a profile for your app in the control panels of nvidia/ati cards.

There are some shapes that are very susceptable to bad anti aliasing even with high settings, narrow spikes and thin cables(think overhead phone/power cables) are amongst this group