AutoCropper 
Standalone script made just for the Hunger Games which automatically takes a screenshot of the full page, crops everything unnecessary, logically names it, saves it in your selected folder and then proceeds to the next day, so you can press the hotkey again. Fastest and most comfortable way to host, while still providing quality pictures. Since Version 3.0.0 also supports automatic updates, custom width, panning, Chrome, Firefox, CSS, non-CSS, custom hotkeys and memorization of all settings.
Firefox Console 
Firefox has a built-in function to take fullpage screenshots which requires no add-on.
Enter screenshot --fullpage --clipboard to copy the screenshot instead of saving it, so you can paste it directly into an image editor.
Full Page Screen Capture 
A Chrome add-on that takes many screenshots while scrolling through the website and then stitches them together to display the result in a new tab. You can then proceed to save the image and close its tab, but cropping has to be done manually.
HostHelper 
Standalone script which let's you choose tributes in threads to automatically add to your game. Upon selection, the avatar's name and image URL are copied to a list, and once the list is full, it gets dumped into the simulator instantly. The script also allows you to comfortably switch the districts of tributes with just three clicks after they're entered on the site. Since Version 2.1 it also automatically checks for updates!
Limit Remover 
A script which removes the 100-character-limit out of events and allows you to still save them. The script only has to be used while adding the event, and then never again.
V1.1 also supports text replacement, so that typing p1 results in (Player1), and so on. List of all available replacements.
HG Customizer 
A userstyle with many customization settings that changes the website inside of the browser. It allows you to set shadows, text size, colors, fonts, image size, background images, Feast/Arena/Fallen Tributes images, and even fixes a bunch of layout faults the site originally had. There's also a new AutoCropper in the description that's compatible with the userstyle. Requires Stylish.
GIMPA free open-source image editor with many capabilities. Recommended.
PhotoshopA too expensive image editor with many capabilities. If you already have it, use this.
Paint.netA free easy-to-use image editor that aims to be an advanced version of MS Paint.
MS PaintThe basic image editor that comes with your installation of Windows. Only really useful for cropping.
8chan Dark Theme 
A dark CSS theme for 8chan made by Rin and Aikawa. To install go to settings → Theme, select Tomorrow as the board theme, and then paste the CSS into the text box and press save.
Dashchan App 
Dashchan is an imageboard client for Android which supports /hga/ and many features. Installation guide: