I noticed that I couldn't kill a process in htop today, F9 did not seem to be working, actualy most of the F-keys did not. The reason turnout out to be that Guake 0.5.0 takes over keys F1 to F10 for direct access to tabs 1 to 10. That may work for most terminal applications, but for htop it's a killer. So how can I prevent Guake from taking F9 over? The preferences dialog allows me to assign a different key, but not no key. Really? There is no context menu, backspace and delete didn't help. For now I assume it's not possible. So I fire up the gconf-editor, menu > Edit > Find... > "guake" — there it is. However, upon "Edit key..." gconf-editor says to me:

Currently pairs and schemas can't be edited. This will be changed in a later version.

Very nice. In the end what did work was to run

gconftool-2 --set /schemas/apps/guake/keybindings/local/switch_tab9 \
    --type string ''

and to restart Guake. I just opened a bug for this. If you like, you can follow it at https://github.com/Guake/guake/issues/376 .