If i want to edit a vimrc file using Textmate I always get this non highlighted flat file.
To have a little bit of colors I select the Shell (Bash) bundle but this is far from perfect for editing vim related files (vimrc, bundles...).
I did some googling of course but only came up with this plugin which still doesn't do syntax highlighting.
You might ask yourself "Why is editing vim stuff without using vim ??" well simply because I am still learning to properly use vim and while learning it I still feel way more comfortable with TextMate.