Some Chrome snippets I like to use.

Snippets.js

// jquerify.js
// https://github.com/bgrins/devtools-snippets
// Add jQuery to any page that does not have it already.
(function () {
  if ( !window.jQuery ) {
    var s = document.createElement('script');
    s.setAttribute('src', '//ajax.googleapis.com/ajax/libs/jquery/2.0.2/jquery.min.js');
    document.body.appendChild(s);
  }
})();

// looknice.js
// Take an unstyled page of text and make it look nicer to read
(function(){
    sty = document.createElement('style');
    sty.innerHTML = 'body{color: #444;font-family: Andalus;line-height: 1.5em;font-weight: normal !important;font-size: 1.2em;}';
    sty.type = 'text/css';
    head = document.getElementsByTagName('head')[0];
    head.appendChild( sty );
})();

// colourer.js
// Colours every element on the page a different crayola colour
(function(){
window.colourer = function( sel ) {
    var colors = [{"hex":"#EFDECD","name":"Almond","rgb":"(239, 222, 205)"},{"hex":"#CD9575","name":"Antique Brass","rgb":"(205, 149, 117)"},{"hex":"#FDD9B5","name":"Apricot","rgb":"(253, 217, 181)"},{"hex":"#78DBE2","name":"Aquamarine","rgb":"(120, 219, 226)"},{"hex":"#87A96B","name":"Asparagus","rgb":"(135, 169, 107)"},{"hex":"#FFA474","name":"Atomic Tangerine","rgb":"(255, 164, 116)"},{"hex":"#FAE7B5","name":"Banana Mania","rgb":"(250, 231, 181)"},{"hex":"#9F8170","name":"Beaver","rgb":"(159, 129, 112)"},{"hex":"#FD7C6E","name":"Bittersweet","rgb":"(253, 124, 110)"},{"hex":"#000000","name":"Black","rgb":"(0,0,0)"},{"hex":"#ACE5EE","name":"Blizzard Blue","rgb":"(172, 229, 238)"},{"hex":"#1F75FE","name":"Blue","rgb":"(31, 117, 254)"},{"hex":"#A2A2D0","name":"Blue Bell","rgb":"(162, 162, 208)"},{"hex":"#6699CC","name":"Blue Gray","rgb":"(102, 153, 204)"},{"hex":"#0D98BA","name":"Blue Green","rgb":"(13, 152, 186)"},{"hex":"#7366BD","name":"Blue Violet","rgb":"(115, 102, 189)"},{"hex":"#DE5D83","name":"Blush","rgb":"(222, 93, 131)"},{"hex":"#CB4154","name":"Brick Red","rgb":"(203, 65, 84)"},{"hex":"#B4674D","name":"Brown","rgb":"(180, 103, 77)"},{"hex":"#FF7F49","name":"Burnt Orange","rgb":"(255, 127, 73)"},{"hex":"#EA7E5D","name":"Burnt Sienna","rgb":"(234, 126, 93)"},{"hex":"#B0B7C6","name":"Cadet Blue","rgb":"(176, 183, 198)"},{"hex":"#FFFF99","name":"Canary","rgb":"(255, 255, 153)"},{"hex":"#1CD3A2","name":"Caribbean Green","rgb":"(28, 211, 162)"},{"hex":"#FFAACC","name":"Carnation Pink","rgb":"(255, 170, 204)"},{"hex":"#DD4492","name":"Cerise","rgb":"(221, 68, 146)"},{"hex":"#1DACD6","name":"Cerulean","rgb":"(29, 172, 214)"},{"hex":"#BC5D58","name":"Chestnut","rgb":"(188, 93, 88)"},{"hex":"#DD9475","name":"Copper","rgb":"(221, 148, 117)"},{"hex":"#9ACEEB","name":"Cornflower","rgb":"(154, 206, 235)"},{"hex":"#FFBCD9","name":"Cotton Candy","rgb":"(255, 188, 217)"},{"hex":"#FDDB6D","name":"Dandelion","rgb":"(253, 219, 109)"},{"hex":"#2B6CC4","name":"Denim","rgb":"(43, 108, 196)"},{"hex":"#EFCDB8","name":"Desert Sand","rgb":"(239, 205, 184)"},{"hex":"#6E5160","name":"Eggplant","rgb":"(110, 81, 96)"},{"hex":"#CEFF1D","name":"Electric Lime","rgb":"(206, 255, 29)"},{"hex":"#71BC78","name":"Fern","rgb":"(113, 188, 120)"},{"hex":"#6DAE81","name":"Forest Green","rgb":"(109, 174, 129)"},{"hex":"#C364C5","name":"Fuchsia","rgb":"(195, 100, 197)"},{"hex":"#CC6666","name":"Fuzzy Wuzzy","rgb":"(204, 102, 102)"},{"hex":"#E7C697","name":"Gold","rgb":"(231, 198, 151)"},{"hex":"#FCD975","name":"Goldenrod","rgb":"(252, 217, 117)"},{"hex":"#A8E4A0","name":"Granny Smith Apple","rgb":"(168, 228, 160)"},{"hex":"#95918C","name":"Gray","rgb":"(149, 145, 140)"},{"hex":"#1CAC78","name":"Green","rgb":"(28, 172, 120)"},{"hex":"#1164B4","name":"Green Blue","rgb":"(17, 100, 180)"},{"hex":"#F0E891","name":"Green Yellow","rgb":"(240, 232, 145)"},{"hex":"#FF1DCE","name":"Hot Magenta","rgb":"(255, 29, 206)"},{"hex":"#B2EC5D","name":"Inchworm","rgb":"(178, 236, 93)"},{"hex":"#5D76CB","name":"Indigo","rgb":"(93, 118, 203)"},{"hex":"#CA3767","name":"Jazzberry Jam","rgb":"(202, 55, 103)"},{"hex":"#3BB08F","name":"Jungle Green","rgb":"(59, 176, 143)"},{"hex":"#FEFE22","name":"Laser Lemon","rgb":"(254, 254, 34)"},{"hex":"#FCB4D5","name":"Lavender","rgb":"(252, 180, 213)"},{"hex":"#FFF44F","name":"Lemon Yellow","rgb":"(255, 244, 79)"},{"hex":"#FFBD88","name":"Macaroni and Cheese","rgb":"(255, 189, 136)"},{"hex":"#F664AF","name":"Magenta","rgb":"(246, 100, 175)"},{"hex":"#AAF0D1","name":"Magic Mint","rgb":"(170, 240, 209)"},{"hex":"#CD4A4C","name":"Mahogany","rgb":"(205, 74, 76)"},{"hex":"#EDD19C","name":"Maize","rgb":"(237, 209, 156)"},{"hex":"#979AAA","name":"Manatee","rgb":"(151, 154, 170)"},{"hex":"#FF8243","name":"Mango Tango","rgb":"(255, 130, 67)"},{"hex":"#C8385A","name":"Maroon","rgb":"(200, 56, 90)"},{"hex":"#EF98AA","name":"Mauvelous","rgb":"(239, 152, 170)"},{"hex":"#FDBCB4","name":"Melon","rgb":"(253, 188, 180)"},{"hex":"#1A4876","name":"Midnight Blue","rgb":"(26, 72, 118)"},{"hex":"#30BA8F","name":"Mountain Meadow","rgb":"(48, 186, 143)"},{"hex":"#C54B8C","name":"Mulberry","rgb":"(197, 75, 140)"},{"hex":"#1974D2","name":"Navy Blue","rgb":"(25, 116, 210)"},{"hex":"#FFA343","name":"Neon Carrot","rgb":"(255, 163, 67)"},{"hex":"#BAB86C","name":"Olive Green","rgb":"(186, 184, 108)"},{"hex":"#FF7538","name":"Orange","rgb":"(255, 117, 56)"},{"hex":"#FF2B2B","name":"Orange Red","rgb":"(255, 43, 43)"},{"hex":"#F8D568","name":"Orange Yellow","rgb":"(248, 213, 104)"},{"hex":"#E6A8D7","name":"Orchid","rgb":"(230, 168, 215)"},{"hex":"#414A4C","name":"Outer Space","rgb":"(65, 74, 76)"},{"hex":"#FF6E4A","name":"Outrageous Orange","rgb":"(255, 110, 74)"},{"hex":"#1CA9C9","name":"Pacific Blue","rgb":"(28, 169, 201)"},{"hex":"#FFCFAB","name":"Peach","rgb":"(255, 207, 171)"},{"hex":"#C5D0E6","name":"Periwinkle","rgb":"(197, 208, 230)"},{"hex":"#FDDDE6","name":"Piggy Pink","rgb":"(253, 221, 230)"},{"hex":"#158078","name":"Pine Green","rgb":"(21, 128, 120)"},{"hex":"#FC74FD","name":"Pink Flamingo","rgb":"(252, 116, 253)"},{"hex":"#F78FA7","name":"Pink Sherbet","rgb":"(247, 143, 167)"},{"hex":"#8E4585","name":"Plum","rgb":"(142, 69, 133)"},{"hex":"#7442C8","name":"Purple Heart","rgb":"(116, 66, 200)"},{"hex":"#9D81BA","name":"Purple Mountain's Majesty","rgb":"(157, 129, 186)"},{"hex":"#FE4EDA","name":"Purple Pizzazz","rgb":"(254, 78, 218)"},{"hex":"#FF496C","name":"Radical Red","rgb":"(255, 73, 108)"},{"hex":"#D68A59","name":"Raw Sienna","rgb":"(214, 138, 89)"},{"hex":"#714B23","name":"Raw Umber","rgb":"(113, 75, 35)"},{"hex":"#FF48D0","name":"Razzle Dazzle Rose","rgb":"(255, 72, 208)"},{"hex":"#E3256B","name":"Razzmatazz","rgb":"(227, 37, 107)"},{"hex":"#EE204D","name":"Red","rgb":"(238,32 ,77 )"},{"hex":"#FF5349","name":"Red Orange","rgb":"(255, 83, 73)"},{"hex":"#C0448F","name":"Red Violet","rgb":"(192, 68, 143)"},{"hex":"#1FCECB","name":"Robin's Egg Blue","rgb":"(31, 206, 203)"},{"hex":"#7851A9","name":"Royal Purple","rgb":"(120, 81, 169)"},{"hex":"#FF9BAA","name":"Salmon","rgb":"(255, 155, 170)"},{"hex":"#FC2847","name":"Scarlet","rgb":"(252, 40, 71)"},{"hex":"#76FF7A","name":"Screamin' Green","rgb":"(118, 255, 122)"},{"hex":"#9FE2BF","name":"Sea Green","rgb":"(159, 226, 191)"},{"hex":"#A5694F","name":"Sepia","rgb":"(165, 105, 79)"},{"hex":"#8A795D","name":"Shadow","rgb":"(138, 121, 93)"},{"hex":"#45CEA2","name":"Shamrock","rgb":"(69, 206, 162)"},{"hex":"#FB7EFD","name":"Shocking Pink","rgb":"(251, 126, 253)"},{"hex":"#CDC5C2","name":"Silver","rgb":"(205, 197, 194)"},{"hex":"#80DAEB","name":"Sky Blue","rgb":"(128, 218, 235)"},{"hex":"#ECEABE","name":"Spring Green","rgb":"(236, 234, 190)"},{"hex":"#FFCF48","name":"Sunglow","rgb":"(255, 207, 72)"},{"hex":"#FD5E53","name":"Sunset Orange","rgb":"(253, 94, 83)"},{"hex":"#FAA76C","name":"Tan","rgb":"(250, 167, 108)"},{"hex":"#18A7B5","name":"Teal Blue","rgb":"(24, 167, 181)"},{"hex":"#EBC7DF","name":"Thistle","rgb":"(235, 199, 223)"},{"hex":"#FC89AC","name":"Tickle Me Pink","rgb":"(252, 137, 172)"},{"hex":"#DBD7D2","name":"Timberwolf","rgb":"(219, 215, 210)"},{"hex":"#17806D","name":"Tropical Rain Forest","rgb":"(23, 128, 109)"},{"hex":"#DEAA88","name":"Tumbleweed","rgb":"(222, 170, 136)"},{"hex":"#77DDE7","name":"Turquoise Blue","rgb":"(119, 221, 231)"},{"hex":"#FFFF66","name":"Unmellow Yellow","rgb":"(255, 255, 102)"},{"hex":"#926EAE","name":"Violet (Purple)","rgb":"(146, 110, 174)"},{"hex":"#324AB2","name":"Violet Blue","rgb":"(50, 74, 178)"},{"hex":"#F75394","name":"Violet Red","rgb":"(247, 83, 148)"},{"hex":"#FFA089","name":"Vivid Tangerine","rgb":"(255, 160, 137)"},{"hex":"#8F509D","name":"Vivid Violet","rgb":"(143, 80, 157)"},{"hex":"#FFFFFF","name":"White","rgb":"(255, 255, 255)"},{"hex":"#A2ADD0","name":"Wild Blue Yonder","rgb":"(162, 173, 208)"},{"hex":"#FF43A4","name":"Wild Strawberry","rgb":"(255, 67, 164)"},{"hex":"#FC6C85","name":"Wild Watermelon","rgb":"(252, 108, 133)"},{"hex":"#CDA4DE","name":"Wisteria","rgb":"(205, 164, 222)"},{"hex":"#FCE883","name":"Yellow","rgb":"(252, 232, 131)"},{"hex":"#C5E384","name":"Yellow Green","rgb":"(197, 227, 132)"},{"hex":"#FFAE42","name":"Yellow Orange","rgb":"(255, 174, 66)"}],
        els = document.querySelectorAll(sel);
    
    for( i in els ) {
        if(els[i].style) els[i].style.backgroundColor = colors[i%colors.length].hex;
    }
};
})();

// YiiUsefulLog.js
// Makes the Yii log a bit more helpful by adding diff times into each row
$($('.yiiLog tr').get().reverse()).each(function(){
  $td = $(this).find('td:first-child'), $comp = $(this).prev().find('td:first-child');
  if( $td.html() && $comp.html() ) {
    $td.append( "<br><strong>" + Math.floor(($td.html().substr(6)*1 - $comp.html().substr(6)*1)*100000)/100000 + "</strong>" );
  }
});'';