Os

[poli]

I have heard this word used as, what I think, is a direct object. This is used in one particular program from Spain. An example would be, [I]os quiero mucho.[/I Further research shows that it can be used as an indirect object as well. Using this pronoun would certainly simplify all the pronoun rules, but at the same time, impede meaning (which os are they referring to?).

Has anyone in this forum heard the use of os before?

[Rusty]

The particular example you posted has a conjugated form of querer, which is a transitive verb. So, the pronoun preceding it can only be a direct object pronoun, and it's a second person plural form, at that, which is used when the referents are familiar (using informal register). Therefore, more than one person is being addressed.

In case you're wondering whether only one (familiar) person could be the referent, I have personally never heard it used that way. (That would be akin to using 'ustedes' while addressing one person, which I would deem ungrammatical.)

Choosing the second person singular direct object pronoun te is correct usage for addressing one person using a familiar or informal register (not 'os'). In a formal situation, the subject pronoun changes to usted (a singular third person pronoun), and lo or la becomes the corresponding direct object pronoun (except in the case of leísmo de cortesía).

Finally, a comparison of direct and indirect object pronouns show that me, te, nos, and os are identical in each set.
However, the other indirect object pronouns are simply le (singular) or les (plural), which seems like an intentional avoidance of gender.

Context (i.e., verb usage, person, number of persons/things, and gender) determines which pronoun gets selected in every case.
And there are resources aplenty about switching any of these to se, when two or more pronouns appear back to back.