Be evil and make people think they've got mail:

/* fake mail */
#mail{
    background: url(%%mail%%);
    position:relative;
    top:2px;
}

#mail img{
    visibility: hidden;
}  

As seen here

A serious amount of creativity and talent went into this - it looks awesome!

Very nicely done ytknows :)

http://www.reddit.com/r/circlejerk

If you have RES and do the konami code, ↑ ↑ ↓ ↓ ← → ← → b a enter, you get flying bacon.

You add your own picture with

#baconBit { 	
position: fixed;
width: 300px;
height: 60px;
background-image: url(%%YOURIMAGE%%);

and slow it down with

  -webkit-transition: all 5s linear !important;
  -moz-transition: all 5s linear !important;
  -o-transition: all 5s linear !important;
  -ms-transition: all 5s linear !important;
  }

Anyone know how to change its direction, make it stop, or just keeping it still?

javascript:void($('.comment').bind('click.z',function(){$.getJSON($('.bylink',c=this).attr('href')+'.json',function(data){$('.md:eq(0)',c).replaceWith('<div%20class="usertext-edit"><textarea>'+data[1].data.children[0].data.body+'</textarea></div>')});$('.comment').unbind('.z')}));

Run the bookmarklet and the next comment you click on will * waves hands * reveal it's secrets.

E: Changed it to a .usertext-edit box from an alert.

E: Fixed: thanks nobody554 for finding a bug and ashleyw for fixing it.

E: People have pointed out Reddit Reveal, which I'm now trying out. The bookmarklet may still be of use if you're not using Firefox or don't want the add-on.

A skydiving reddit alien made for /r/skydiving. Scroll down to see him jump, hover to launch his parachute.

javascript:void($.getJSON($('.user%20a').attr('href')+'/about.json',function(u){alert(new%20Date(u.data.created*1000))}));

Inspired by this.

See it here

The syntax is [spoiler](/s"This is a secret") and it just acts as a link when styles are disabled, preventing accidental viewing.

Here is the css:

 /* spoiler */

a[href="/s"]{
    font-size: 0;
    cursor: default;
    visibility: hidden;
}

a[href="/s"]::after{
    content: attr(title);
    background: black;
    color: black;
    font-size:small;
    padding: 0 0.5em 0 0.5em;
    visibility: visible;
}

a[href="/s"]:hover::after, a[href="/s"]:active::after{
    color: white;
}

  x=$('.entry').filter(function(){return($.inArray($('.author:first',this).text(),['list','of','douchebags','here'])!=-1)});x.prev().hide();x.hide();

Inspired by this.
x.prev().hide() is to get rid of the vote buttons for the hidden posts.

E: Or there's Reddit Filter Plus.

I have created this reference for people to use. I have been continually frustrated with how capricious the designers of reddit chose to be, in how they display various subreddits on the "edit" page. My list, on the other hand, is ordered strictly by the number of subscribers a subreddit has.

My list is here.

Here's a screenshot since it probably won't stay that way for too long. Kudos to everyone who has contributed. I've learned quite a lot from reading the posts and comments here. Thanks!

MUCH appreciated. Need it fairly quick, too