Most small creatures are not aggressive and have no wish to bite or sting, those than can normally only doing so when threatened.  Many will happily rest on us, often  doing so voluntarily appreciating the warmth.  A tiny number of species bite for a tiny amount of our blood which they need to be able to breed, but of all the following, that only applies to one which I chose to allow in order to get the photo.  Click any photo to enlarge.