When it comes to synonyms for "flag one," many options are available. Depending on the context, possible alternatives may include "highlight," "note," "mark," "indicate," "designate," "point out," or "signal." While they all have slightly different connotations, each suggests drawing attention to something specific. For instance, "highlight" may emphasize an important factor, while "signal" may suggest a deliberate attempt to communicate a message. Ultimately, the best choice will depend on the specific usage and desired emphasis. Still, with such a wide range of options available, there's sure to be a suitable synonym for any context.