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

BlockHole.css

/* Install the Stylish extension for your browser, then add this code
as a new Style. Make sure it applies 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. */

/* Thanks to: @pbausch, @mathowie, @blakestacey, @ukuleledan and others! */

/* Hide the heart for un-Faved tweets. */
.ProfileTweet-actionButton .HeartAnimationContainer {
  visibility: hidden;
}

.WebToast .HeartAnimationContainer {
  visibility: hidden;
}

/* Specify an emoji to use in place of the heart, for un-Faved tweets. */
.ProfileTweet-actionButton .HeartAnimationContainer:after {
  /* Use a grayed-out emoji for the unclicked Fav button. */
  content:'🍺';
  /* Safari or Chrome */
  -webkit-filter: grayscale(100%);
  opacity: 0.7;
  /* Firefox or Mozilla */
  /* -moz-filter: grayscale(100%); */
  visibility: visible;
  display: block;
  position: absolute;
}

/* Show the regular emoji when hovering over the fav button. Via @mrtnrs_ on twitter. */
.ProfileTweet-actionButton .HeartAnimationContainer:hover:after {
  /* Use a regular emoji for the hovered Fav button. */
  content:'🍺';
  /* Safari or Chrome */
  -webkit-filter: grayscale(0%);
  /* Firefox or Mozilla */
  /* -moz-filter: grayscale(50%); */
  visibility: visible;
  display: block;
  position: absolute;
}

/* Hide the heart for Faved tweets. */
.ProfileTweet-actionButtonUndo .HeartAnimationContainer {
  visibility: hidden;
}

/* Replace the heart for Faved tweets with an emoji. */
.ProfileTweet-actionButtonUndo .HeartAnimationContainer:after {
  /* Use a regular emoji for the clicked Fav button. */
  content:'🍺';
  visibility: visible;
  display: block;
  position: absolute;
}

/* Change the text color for the Fav count. */
.ProfileTweet-actionCountForPresentation {
 color: #999;
}

/* ----------------------------------------------------------- */
/* The following code changes icons in the Notification Stream */
/* ----------------------------------------------------------- */

/* Hide the heart icon for Favs in the notification stream. */
.activity-type-favorite {
 visibility: hidden;
}

/* Replace them with an emoji. */
.activity-type-favorite:before {
  content:'⭐️'; 
  visibility: visible;
  display: inline-block;
  position: relative;
  vertical-align: middle;
  line-height: 18px;
  font-size: 15px;
}

/* Hide the icon for a retweet in notification stream. */
.activity-type-retweet {
 visibility: hidden;
}

/* Replace it with an emoji. */
.activity-type-retweet:before {
  content:'💯'; 
  visibility: visible;
  display: inline-block;
  position: relative;
  vertical-align: middle;
  line-height: 18px;
  font-size: 15px;
}


/* Hide the icon for a favorited mention in notification stream. */
.activity-type-favorited_mention {
 visibility: hidden;
}

/* Replace it with an emoji. */
.activity-type-favorited_mention:before {
  content:'🔥'; 
  visibility: visible;
  display: inline-block;
  position: relative;
  vertical-align: middle;
  line-height: 18px;
  font-size: 15px;
 }

/* Hide the icon for a favorited retweet in notification stream. */
.activity-type-favorited_retweet {
 visibility: hidden;
}

/* Replace it with an emoji. */
.activity-type-favorited_retweet:before {
  content:'⚡️'; 
  visibility: visible;
  display: inline-block;
  position: relative;
  vertical-align: middle;
  line-height: 18px;
  font-size: 15px;
}

/* Hide the icon for a retweeted retweet in notification stream. */
.activity-type-retweeted_retweet {
 visibility: hidden;
}

/* Replace it with an emoji. */
.activity-type-retweeted_retweet:before {
  content:'💯'; 
  visibility: visible;
  display: inline-block;
  position: relative;
  vertical-align: middle;
  line-height: 18px;
  font-size: 15px;
}

/* Hide the icon for a new follower in notification stream. */
.activity-type-follow {
 visibility: hidden;
}

/* Replace it with an emoji. */
.activity-type-follow:before {
  content:'😄'; 
  visibility: visible;
  display: inline-block;
  position: relative;
  vertical-align: middle;
  line-height: 18px;
  font-size: 15px;
}

/* ------------------------------------------------------------- */
/* This code changes "Likes" to "Favorites" on the Profile Page. */
/* ------------------------------------------------------------- */

/* Remove 'Likes' on Profile Page */
.ProfileNav-item--favorites .ProfileNav-label {
  visibility: hidden;
}

/* replace it with 'Favorites' */
/* Thanks to @pbausch and @mathowie for a fix here! */
.ProfileNav-item--favorites .ProfileNav-label:after {
  content:'Favorites'; 
  visibility: visible;
  margin-left: -30px;  
}

/* ------------------------------------------------------------- */
/* Tired of clicking 'Moments' when you tried to click on        */
/* 'Notifications'? Hide the 'Moments' tab.                      */
/* ------------------------------------------------------------- */

/* via Izzy Galvez @iglvzx on twitter. */
/* https://twitter.com/iglvzx/status/672900709596049408 */
.global-nav .moments {
    display: none;
} 

/* ------------------------------------------------------------- */
/* Ever feel like 'blocking' isn't enough? Why not drop that     */
/* troll into a black hole?                                      */
/* ------------------------------------------------------------- */

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

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

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