Change "Block" to "Drop Into Black Hole" in a Twitter account's dropdown action menu.

BlockHole.css

/* Install the Stylish extension for your browser, add this code
as a new Style, and apply it to the domain 'twitter.com' */

/* You can get Stylish here: */
/* Safari - http://sobolev.us/stylish/ */
/* Chrome - https://chrome.google.com/webstore/detail/stylish/fjnbnpbmkenffdnngjfgmeleoegfcffe */

/* Tweet improvements, comments, or corrections to @mcnees. */

/* ------------------------------------------------------------- */
/* Ever feel like 'blocking' isn't enough? Why not drop that     */
/* troll into a black hole? Change the Mute, Block, and Report   */
/* text to something else.                                       */
/* ------------------------------------------------------------- */

/*--------( Block )--------*/
/* Hide the 'Block' text in the user drop-down menu. */
.block-link button {
  visibility: hidden;
}

/* Replace the text with 'Drop Into Black Hole'. */
.block-link  button:before {
  content:'Drop Into Black Hole';
  visibility: visible;
}

/* Make sure the background color changes when hovered over. */
.block-link:hover  {
  background-color:#0084B4;
}

/*--------( Mute )--------*/
/* Hide the 'Mute' text in the user drop-down menu. */
.mute-user-item button {
  visibility: hidden;
}

/* Replace the Mute text with 'You Be Quiet'. */
.mute-user-item  button:before {
  content:'You Be Quiet';
  visibility: visible;
}

/* Make sure the background color changes when hovered over. */
.mute-user-item:hover  {
  background-color:#0084B4;
}

/*--------( Report )--------*/
/* Hide the 'Report' text in the user drop-down menu. */
.report-text button {
  visibility: hidden;
}

/* Replace the Report text with 'Summon Great Old Ones'. */
.report-text  button:before {
  content:'Summon Great Old Ones';
  visibility: visible;
}

/* Make sure the background color changes when hovered over. */
.report-text:hover  {
  background-color:#0084B4;
}

Here's a link to equivalent code for Tweetdeck: https://gist.github.com/noamross/f12e39816ba2f398c580

The style should look something like this: