People with blood type O always put rationality first, and have two sides, sometimes silent and sometimes very planned. So you must pay attention to rationality when giving gifts.
But it also depends on what zodiac sign it is, and the real situation of the person. If your boyfriend is a more casual person, you can give him a necklace, such as a tungsten steel personalized military card, which can be engraved for free, and you can choose the chain yourself, such as an O-shaped chain, a leather rope, a letter chain, etc. Engrave your name, birthday or motto on it.
If your boyfriend is a rigorous person, you can give him a fountain pen, which is a very tasteful gift. When choosing a fountain pen, you should look at its smoothness of writing and the quality of the fountain pen. Generally, most people look at the appearance and want to buy a fashionable and powerful gift.