core/homeassistant/components/button/icons.json

{
  "entity_component": {
    "_": {
      "default": "mdi:button-pointer"
    },
    "restart": {
      "default": "mdi:restart"
    },
    "identify": {
      "default": "mdi:crosshairs-question"
    },
    "update": {
      "default": "mdi:package-up"
    }
  },
  "services": {
    "press": {
      "service": "mdi:gesture-tap-button"
    }
  }
}