There are a lot of feature-request's on Meta that seem useful. I've gone through some of them, and made one userscript to add some, or all of them:

Features added (go to Github to see their descriptions):

• Fixed Topbar (v0.1)
• Unfade low score answers (v0.1)
• Move show more comments link to top (v0.1)
• Ellipsis after long names (v0.1)
• Rename chat tabs (v0.1)
• Move start a bounty to after the question (instead of after comments) (v0.1)
• Make the bounty box draggable (v0.1)
• Fade out vote signs on deleted answers (v0.1)
• Replace > bullet points with more normal ones (v0.1)
• Differentiate between employees¹ (v0.1)
• Remove exclamation mark on error (v0.1)
• Highlight only the tags for your 'favourite questions' (v0.3)
• Show your username in the topbar (v0.3)
• Colour the answerer's names in comments (v0.4)
• Add KBD and Bullet options in editor toolbar (v0.4) - alt + k / alt + l
• Add pre-defined edit reason checkboxes on edit pages (v0.4)
• Change the 'share' link to show link as markdown format (v0.5)
• Add Ctrl+i,b,k support to comment fields (v0.5)
• Add a button to reveal spoilers in a post (v0.5)
• Highlight on hold/closed questions (v0.7)
• Add shortcuts for adding pre-defined comments (v0.7)
• Differentiate between empty blockquotes and spoilers (v0.7)
• Add reply links for quick replying (v0.8)
• Parse cross-site links to questions (v0.8)
• Show answer counts on sidebar (v0.9)
• Button to add author's name to hyperlinks (v0.9)
• Confirm when navigating away if you have started writing a comment (v1.0)
• Allow you to sort bounties by their amout (v1.0)
• Add a label when the question you are viewing is a 'hot-network question' (v1.1)

In this script, I've made everything optional. You choose what you want - if you hate the fixed topbar (which it seems a lot of you do...), disable it!. The options are saved via GM_setValue².

The script

It's on Github over here.

Please post any feature requests (along with their meta link, if applicable) and bug reports (along with any errors in console, if applicable)!

I've only tested it on Google Chrome - please tell me if you find any compatibility issues. You need to have something like Greasemonkey or Tampermonkey or Scriptish to be able to use the script because it relies on GM_* functions.

¹This is a flawed idea right now, it might call a normal user an employee (hence the tooltip 'possible employee'), but basically, there's a list of names in an array and the script checks for names and sees if the name is in the array. If it is, a star (★) is added after their name:

²You will be asked to set the options if you browse on an SE site without them already being set. If you want to change the options, a link is displayed (add features) on your profile. Clicking it will show a box for you to choose the options you want and save them.

Change Log:

• 15/01/15 - v0.2: Switched from cookies to GM setValue (thanks for idea @BrockAdams)
• 16/01/15 - v0.3: Added more features (mentioned above)
• 25/01/15 - v0.4: Added more features (mentioned above)
• 22/02/15 - v0.5: Added more features (mentioned above), minor bug fix
• 28/02/15 - v0.6: Bug fixes (thanks @IlmariKaronen):
  • Works on Firefox now
  • unspoil feature updated
  • Popup now shows in centre of screen
  • Show descriptions after checkbox
  • Update checkbox values to saved settings when you open the dialog box
  • No more auto-delete settings after you open the dialog box
  • No annoying alert when you don't choose any options / save the options
  • Renamed save button
  • Compatibility with new (currently MSE-only) profiles
• 06/03/15 - v0.7: Added more features (mentioned above)
• 22/03/15 - v0.8: Added more features (mentioned above)
• 26/03/15 - v0.9: Added more features (mentioned above), updated kbdAndBullets function to make icons fit better
• 29/03/15 - v1.0: Added more features (mentioned above)
• 30/03/15 - v1.1: Added more features (mentioned above)