In the context of a video game menu, which has a selection/button labeled "PLAY!" which when pressed will take the user from the menu into a new game, what would be the correct Spanish translation? Should it be "¡JUEGA!"? Or maybe "¡JUEGUE!"?
Interesting, both could work but, as a gamer, I've often seen ¡juega! instead of using the subjunctive. But I wouldn't be surprised if I saw the instruction given as ¡juegue!, it sounds a little weird to my ears though.
However, base forms in English are often translated with the infinitive in Spanish, namely play! = ¡jugar!
"Juega" is the imperative form of the verb: "Juega tú".
"Juegue" is also the imperative form of the verb: "Juegue usted".
It is easily seen that both forms are the second person of the singular on imperative tense, with "juega" associated with the informal "tú" and "juegue", coincident in form with the third person, associated with the more formal "usted". From these, a third form arises:
"Jugá" is the imperative form of the verb: "Jugá vos"
This third form is the standard in zones with the "voseo" characteristic.
So, the answers suggesting to use the infinitive "Jugar" are wrong (as most of the game translations out there). The english "Play" is an imperative, not an infinitive which would be written as "To play".
But still, the question is not answered, as we have seen that all three ("Juega", "juegue", "jugá") are valid. From these, you need to choose taking in account the zone of the Spanish world for which you are translating.
In Argentina and nearby zones, it will be always "jugá".
In Spain, if you are formally addressing the player, it will be "juege", but if you are addressing him unformally (as usual in most electronic means, but not necessarily correct) it will be "juega".
In most zones of the Americas, it will be always "juega".
Recommendation: to make one single translation, use "juega".