I like this translation with its ambiguous head noun, since it also means “Beware the gifts that a Greek brings you,” which would have been a far more appropriate warning to the Trojans.

For a long time, I’ve felt that when context doesn’t make the head noun obvious, the Relative Clause could have the valid translation, “Beware Greeks and/or the gifts they give you.” Just because there is no conjunction in the original, that doesn’t mean the translation wouldn’t be accurate.