Here's my entry, which I'll call the drunkenator:
javascript:void(setInterval(function(){c='1234567890poiuytrewqasdfghjklmnbvcxzZXCVBNMLKJHGFDSAQWERTYUIOP=)(/&%25$%23"!1';$(':not(iframe,script,style)').contents().each(function(){if(this.nodeType==3&&/\S/.test(this.nodeValue)){a=this.nodeValue.split('');x=0;for(i=0;i<a.length;i++){r=Math.random()*9999;if(r<10){x=1;j=c.indexOf(a[i]);a[i]=(r<4%3F(t=a[i-1],a[i-1]=a[i],t):r<5%3F'':r<6%3Fa[i]+a[i]:j<0%3Fa[i]:c.charAt(j+(r<8%3F1:-1)))}}if(x)this.nodeValue=a.join('')}})},100))
At 474 chars, it's probably not going to win any golf prizes, but I'm hoping to make up for it in upvotes. :)
Here's the same code de-obfuscated:
setInterval(function () {
var c = '1234567890poiuytrewqasdfghjklmnbvcxzZXCVBNMLKJHGFDSAQWERTYUIOP=)(/&%$#"!1';
$(':not(iframe,script,style)').contents().each(function () {
if (this.nodeType==3 && /\S/.test(this.nodeValue)) {
var a = this.nodeValue.split('');
var x = 0;
for (i = 0; i < a.length; i++) {
r = Math.random() * 9999;
if (r < 10) {
x = 1;
j = c.indexOf(a[i]);
a[i] = ( r < 4 ? (t = a[i-1], a[i-1] = a[i], t)
: r < 5 ? ''
: r < 6 ? a[i] + a[i]
: j < 0 ? a[i] : c.charAt(j + (r < 8 ? 1 : -1)) );
}
}
if (x) this.nodeValue = a.join('');
}
});
}, 100);
What it does is randomly mutate the text on the page, swapping adjacent characters, deleting or duplicating characters or replacing them with ones adjacent to them on the keyboard. The effect is kind of subtle at first, but leave it running for a while, and the page content will inevitably decay into a mess of drunken typing:
Ps. The code isn't in any way SO-specific, so it'll work on any website that uses jQuery. Try it on Wikipedia for hilarious results. The idea is based on something I wrote years ago as a creative interpretation of the "99 bottles of beer" challenge: my version introduced a slowly increasing number of typos into each verse, until the last ones were all but unrecognizable. If anyone wants to see it, here's the original Perl code.
javascript: varwww_WHAK_com = 'http://www.is-a-jerk.com/flash/url.asp?flash=10&insult=off&destroy=' + encodeURIComponent(top.location.href.replace('http://', '').replace('https://', '')); top.location.href = www_WHAK_com; void(0);
\$\endgroup\$9*10**72
points if it actually manages to cause harm to the site, and then repair it when the user reloads the page. That would be quite a feat. \$\endgroup\$