Please don't pray for me; instead, put that time to better use by donating blood. How long would a prayer be about me? It has been a while since I prayed last, but I would imagine a "good" prayer would be about two minutes (unless you do it half-heartedly). I am estimating two minutes as you must pray for God to shine light on me, Jesus to enter my heart, let me realize the wickedness of my ways, etc. And how many times would you pray for me? Does it take just one prayer to save me, or would you include me in your nightly prayers for a week?
Let's assume the latter case. So, you would spend about 10-15 minutes to pray for me in a week. Why not put that time to actual use and donate blood? Blood donation takes 7-10 minutes. If your God hasn't revealed Himself to me like he has done so for you, obviously he doesn't want me to believe in Him anyway, so why try to change his mind? And even if your prayers succeeded, that took 10-15 minutes to save one person. Had you taken 7-10 minutes of that time, you could have donated a pint of blood which could have saved three people. If you're a good bleeder, you could have donated two pints within 15 minutes, and thus saved six people.
It just adds up: blood donation > prayer.