Comedown is both physical and mental.
Examples of drugs which will have a strong physical comedown are alcohol (obviously) which will probably leave you with a headache and sometimes aching joints.
Many drugs will leave you with both physical and mental punishment.
Ecstacy will do this, the physical is often magnified by the fact that many xtc users will be raving or clubbing so the body gets overtired, but you will also become scattered. In other words, it will feel like the electric impulses in your brain are dull and you will generally feel lost, confused, and depressed.

There are also drugs which will leave you with a primarily metal come down, shrooms are an example of this, because they are extremely taxing on the mind.

Earlier in this write up i mentioned that drugs punish you.
I said this because I see comedown as a form of punishment for doing something bad for you.
In other words, what goes up, must come down.

Further, although this stage is called 'come down ' it can also be seen as a come up .
By this i mean that your body comes down in a short space of time, then spends several hours after that trying to come back up, and bring itself to speed.

It can also be noted that comedowns are relative. The more psychoactive the drug you take, often your mind will be tired afterwards, if the drug induces more of a physical effect for example speed, your physical state will be more affected in comedown.