Learn German: Jeder Neuling bekommt eine Waffe. - Every newcomer gets a weapon.

Jeder must agree with the gender of Neuling. Nouns that end in the suffix -ling are predictably masculine (der Neuling). Because it is the subject of the sentence (nominative case), the word for "every" takes the masculine nominative ending -er.

How would you say "All newcomers get a weapon" to see the plural form of Neuling in action?

You would say: Alle Neulinge bekommen eine Waffe. Nouns ending in the suffix -ling have a very predictable and regular plural: you simply add an -e to the end.

Are there other common words built the exact same way as Neuling?

Yes, the suffix -ling is often added to adjectives or verb stems to describe a person or thing characterized by that trait. For example, feige (cowardly) becomes der Feigling (coward), and prüfen (to examine) becomes der Prüfling (examinee). They are all masculine and take an -e in the plural.

I sometimes mix up jeder, jeden, and jedem. Is there a quick trick to confirm why it is jeder here?