First off, my O negative blood makes me a universal donor. Under 7% have this blood type, which can be given to someone of any other blood type (especially in trauma situations when the blood type of the recipient is unknown).
But beyond that, my blood is CMV negative. That means I have never been exposed to
a common virus (cytomegalovirus) that is dangerous to newborns. Along with other donation limitations, this makes me an elite universal baby donor. Less than 1 out of 200 people qualify, and most are oblivious to this gift. Needless to say, the Red Cross calls me regularly so I get my butt in and donate every 56 days.
Of course, we follow a suffering servant who was (and continues to be) a real universal blood donor, bearing a unique gift of life. Lying down in a climate-controlled room bleeding out a carefully measured pint doesn't begin to approach that, but still, it feels like something sacramental is going on in those rooms. Physically giving part of our bodies to literally save a life... wow.
For all our focus on the Blood of Christ I'm surprised how rarely Catholic parishes promote blood drives (kudos if yours does!). Try donating if you are physically able, regardless of your blood type (all are needed). If you already donate, next time bring someone along. Promote it within your parish (the Solemnity of the Body and Blood of Christ is June 22!). The gift of blood is the gift of life!