Different families of proteins that linked because they perform recognizably similar classes of work, even if unrelated by protein homology, form a guild of protein families. In a typical bioinformatics grammar, a key feature may be the presence of a protein (or cluster of proteins) from a particular guild rather than from a particular protein family.
CRISPR-associated proteins form a guild (PMID:16292354).
Capsular biosynthesis enzymes in bacteria form a guild.
Bacteriocin maturation proteins or, more generally, ribosomally translated natural product maturation proteins, form a guild.
Type 2 toxin-antitoxin systems occur as a tandem pairing of a member of the guild of toxins with a member of the guild of antitoxins (see PMID:19493340).