Copy and paste in the console of a page without jquery to load jquery. Leaves no artifacts of itself once it executes.

load_jquery.js

// loading jQuery on a site that doesn't have jquery for fun and ... hmmm profit?.

(function (jQueryURL) {

    function loadSuccess() {
        eval(this.responseText);
        console.log("jQuery loaded.");
    }

    function loadFailed(event) {
        console.log("Failed to load jQuery source.", event);
    }

    if(window.jQuery) {
        console.log("jQuery " + $.fn.jquery + " already loaded.");
        return;
    }

    var request = new XMLHttpRequest();
    request.addEventListener("load", loadSuccess, false);
    request.addEventListener("error", loadFailed, false);
    request.open("GET", jQueryURL, true);
    request.send();
    
})("https://code.jquery.com/jquery-2.1.4.js");