Enumerable.Range
Tends to be underused. Starts with a given value and generates a number of sequential values.Enumerable.Range(0, 5) => { 0, 1, 2, 3, 4 }
Enumerable.Repeat
Also underused. Repeats a value n times.Enumerable.Repeat("X", 5) => { "X", "X", "X", "X", "X" }