The perfect wedding gift

I and my co-workers are discussing what we should give our co-staff nurse as a gift for his wedding day. We have agreed on a certain budget but since they do not have wedding registry and we are too shy to ask what they would want for their big day, we are seriously having headaches thinking of a very useful gift that they would cherish. Gifts under $100 are the ones that we are considering. We hope that we could chose one before the big day.