Whitespace
Wikipedia: Whitespace (programming language)
Online Interpreter to Test Answer
The program pushes the ASCII character codes through the following steps (taken from the interpreter debug sidebar):
push 72 printc push 101 printc push 108 printc push 108 printc push 111 printc push 32 printc push 87 printc push 111 printc push 114 printc push 108 printc push 100 printc push 33 printc end