Calculated Number Field is a calculated custom field returning a number (integer or float). It is a read-only field that returns the result of the evaluation of a formula, such as the addition of two other fields. View details here.

Calculated Text Field (new in 1.5.5) is a calculated custom field returning a String. It is a read-only field that returns the result of the evaluation of a formula, such as the concatenation of two other fields. View details here.

Exact Text Searcher (Statistics-compatible) is a custom searcher that allows calculated text fields to be used in statistics gadgets. View details here.

Calculated Date/Time Field is a calculated custom field returning a java.util.Date (which represents a date+time). It is a read-only field that returns the result of the evaluation of a formula. View details here.

Transition Date/Time Field is a calculated custom field returning the date and time of the last execution of a specified workflow transition. View details here.

Transition Caller Field (new in 1.2) is a calculated custom field returning the caller of the last execution of a specified workflow transition. View details here.

Transition Count Field is a calculated custom field returning the number of times a specified workflow transition was executed. View details here.

Last Field Value Change Date/Time Field is a calculated custom field returning the date and time a field was last modified. View details here.

Parent Status Field is a calculated custom field returning the Status of the issue's parent issue. View details here.

currentUserPropertyAsList is a JQL function that returns the value of a property of the current user, transforming comma-separated values into a list of values. View details here.