What is the standard issue military equipment?

This depends on which military organization you are asking about. Standard equipment will be different, for example, for the Belgian Army than for the army of Malawi.

For the US Arms, the short and simple answer is "to read Common Tables of Allowances 50-900 (Clothing and Individual Equipment), 50-909 (Field and Garrison Furnishings and Equipment) and 50-970 (Expendable/Durable Items)."

The real answer is that there is no such thing as "standard issue military equipment." Every unit, and sometimes every part of a unit, has different equipment. I'll give you an example: I was in three tactical units: the 101st Airborne Division, III Corps and the 10th Mountain Division. When you report to a unit they send you to Central Issue Facility to draw field equipment. The issue at those three places was completely different--the 101st gave me a smaller pack than the other two places, III Corps gave me mechanic's coveralls and the 10th Mountain gave me a $1500 arctic uniform.