There are some catches, though, and commonly there is no completely Erg-abs language. In fact Erg-abs marks the Subject of intransitive as objects of transitive, but Nom-acc does not mark Subjects of intransitive as Objects of transitive verbs. Or even sometimes an Erg-abs marks objects of transitive verbs different from Subjects of intransitive ones, the case of Basque. So you have these two types (plus their counter-versions) and the Tripartite (to mark them all), although I must say this is if you want to keep it reasonably simple.
I wanted to make something different for one of my languages, which I’m calling Unnai for now. In this language nouns are invariable for case, but the verb is conjugated according to the morphosyntactic alignment you chose to follow.
ölön to hear
ölögno Nom-acc intrasitive or omiting object of transitive
ölöngon Nom-acc transitive
ölöjnen Abs-erg transitive or omiting subject of transitive
Of course you have to use the pronouns accordingly. And depending on the verb alignment then can shift places without changing their meaning.
ölöngon shag ghal I hear you
ɛlˈɛngon ʃag ɣal
ölöjnen ghal shag I hear you
ɛlˈɛd͡ʒnen ɣal ʃag
It is noteworthy to mention that both sentences mean the same, although Unnai has no passive voice. In those cases where passive voice would be used Unnai uses the second construction to express it, since you can leave aside the subject of the verb ölöjnen ghal would mean “(someone) hears you” or, what’s the same, “you are heard (by someone)”. So adding the subject here would be pretty equivalent to adding the agent in a passive construction.