Have you tried sending the special characters like this
Keyboard.set_key1(KEY_TILDE);
Keyboard.send_now();
Keyboard.set_key1(0); // reset key state
Keyboard.send_now();
Other keycodes here http://www.pjrc.com/teensy/td_keyboard.html
Short of this, you could poke around in path\hardware\teensy\cores\teensy_hid