Thaumaturgy. Nothing major, just enough to slightly change aspects of my surroundings at will. Someone tailgates me while driving, now their check engine light is on and their engine is making a weird, undiagnosable noise. A man cat calls me, he now has an unscratchable itch. A kid is upset, now they suddenly taste candy. I feel like there's so much good or evil that could he done by making nearly undetectable changes to the physical world.