http://hce.halomaps.org/index.cfm?search=string+list+editor&B1=Search Take your pick: SteelIBX's, or E3Po's String List Editor
read the readme
use it to edit "tags\ui\hud\hud_icon_messages.unicode_string_list"
Edit the vehicle tag's "hud text message index" to be the line number you changed/added
Quote: Basically this little utility allows you to do what guerilla doesn't - edit unicode_string_lists. You can also export to a regular string list txt file (ascii or unicode), and compile in tool, but there really isn't much point since this utility also saves string lists.
So what is the use for this exactly? Well first of all you can easily add more strings for weapons like 'Picked up a Grenade Launcher', you can change various other text too like %s was pwned by %s, and more strings for new vehicles, such as 'Press E to enter drivers seat of Goliath'
How to use:
1. Open a string_list / unicode_string_list tag. Edit as you think appropriate, save tag.
2. Compile your map
NOTE: If your string list is (for some reason) the same filesize as the old one, tool will not compile it into your map, in which case you should maybe add a blank item to the list at the end, or change the length of an item with extra spaces.