The variable adaptive-wrap-extra-indent from adaptive-wrap.el in ELPA
should be a safe as a file local variable.  It can be useful to set as a
file local and shouldn't pose any danger from untrusted files.

diff --git a/packages/adaptive-wrap/adaptive-wrap.el
b/packages/adaptive-wrap/adaptive-wrap.el
index 9455789..01024de 100644
--- a/packages/adaptive-wrap/adaptive-wrap.el
+++ b/packages/adaptive-wrap/adaptive-wrap.el
@@ -57,6 +57,7 @@ extra indent = 2
   :type 'integer
   :group 'visual-line)
 (make-variable-buffer-local 'adaptive-wrap-extra-indent)
+(put 'adaptive-wrap-extra-indent 'safe-local-variable 'integerp)

 (defun adaptive-wrap-fill-context-prefix (beg en)
   "Like `fill-context-prefix', but with length adjusted by
`adaptive-wrap-extra-indent'."

-- 
Thanks,

Jonathan Kotta

Hofstadter's Law:
    It always takes longer than you expect, even
    when you take into account Hofstadter's Law.