The Purdue Remote Online Computer System (PROCSY) was a Fortran program that interpreted scripts line at a time. A few dozen primitive commands was about it. However command arguments could include substituted string parameters with optional defaults.
Backward Jumps through a recursive call with a computed jump forward as the first line.
Repeatedly Folded Arithmetic with long sequences of if statements encoding addition tables. These are repeatedly folded over upon themselves with parameters distinguishing the folds. Eventually a few dozen lines can count through machine addresses.
Denial of Service Gone Wrong when a tight loop starves service from other terminals. I'd lock up the cpu for 10, 20 and then 60 seconds. First a few teletypes stopped printing, then most teletypes, and then all teletypes. And they never came back. The seconds counter wrapped around at 59. Oops.
Interactive Football where two players would take turns calling plays.
Hangman played a graphical version of the child's game by emitting canned strings interpreted by Bill Croft's graphically augmented terminal program. This was coded in PROCSY, a remote batch control language never meant for graphics.
Pfiles Get/Put short-cuts for saving and recalling multiple local files in a single command.