Five is a low number, might be better to try and get up to 7 or 8.
Failing that I might pick - in no particular order:
Jouney to Babel
The City on the Edge of Forever
The Galileo Seven
The Trouble with Tribbles
Balance of Terror
Although I might also pick (on different days) from the likes of - The Devil in the Dark, Wolf in the Fold, Court-Martial, The Conscience of the King, The Empath, The Tholian Web and Where No Man Has Gone Before.
'If the Apocalypse starts, beep me!' - Buffy Summers
'The sky's the limit.....' Jean-Luc Picard, 'All Good Things'
courtesy of Saquist