Better override

(defvar custom-keys-mode-map (make-keymap) "custom-keys-mode keymap.")
(define-minor-mode custom-keys-mode
  "A minor mode so that my key settings override annoying major modes."
  t " my-keys" 'custom-keys-mode-map)
(custom-keys-mode 1)

(defun my-minibuffer-setup-hook ()
  (custom-keys-mode 0))
(add-hook 'minibuffer-setup-hook 'my-minibuffer-setup-hook)

(defadvice load (after give-my-keybindings-priority)
  "Try to ensure that my keybindings always have priority."
  (if (not (eq (car (car minor-mode-map-alist)) 'custom-keys-mode))
      (let ((mykeys (assq 'custom-keys-mode minor-mode-map-alist)))
        (assq-delete-all 'custom-keys-mode minor-mode-map-alist)
        (add-to-list 'minor-mode-map-alist mykeys))))
(ad-activate 'load)
(define-key custom-keys-mode-map (kbd "<C-key>") 'some-command)