A Kate syntax highlighter for common bbcode. Includes emoticon highlighting for the GiantITP forums.
If you are using KDE 5, place the file bbcode.xml in the folder ~/.local/share/katepart5/syntax. If you are using KDE 4, place it in the folder ~/.kde/share/apps/katepart/syntax. The folder may not exist. If so, create the folder.
Once the file is in place, restart Kate. Save a bbcode-markup text file with the extension .bbcode to see the effect.