Other forms: requisites
Requisite is a formal or fancy word for indispensable. During your punk phase, you refused to leave the house without the requisite leather jacket, black boots, and mohawk.
To remember this word, notice how similar it is to required. College students looking to sign up for classes they find interesting often bump up against the word prerequisite, which refers to a list of classes they will need to take before the one they're interested in.