To find \( f(6) \) given that \( f(x) = -x^2 - 14 \), we simply substitute \( x = 6 \) into the function:
\[ f(6) = -6^2 - 14 \]
Calculating \( 6^2 \):
\[ 6^2 = 36 \]
Now, substituting back into the function:
\[ f(6) = -36 - 14 \]
Combining the values:
\[ f(6) = -50 \]
Thus, the value of \( f(6) \) is \( \boxed{-50} \).