Which proof of God's existence was most convincing to you?

Dr Kreeft's Handbook, which is the subject of several threads below, lists 20 "arguments," that have been suggested over the years. But before he begins his list, he says: "You may be blessed with a vivid sense of God's Presence; and that is something for which to be profoundly grateful."
I struggle to imagine what other proof could be more important and effective, especially when you also feel God's Love, and would be grateful to hear experiences of others.