Q:

Find the most important character

Find the most important character
The challenge is to write a program that outputs the most occurrent character in the input string, excluding these bracketing characters ()[]{}.   Each submission should consist only of non-trivial* characters.   Each solution is scored using the formula in the scoring section.   Bracketing characters are allowed in the program, but may not be selected by the program as the most occurrent character.   In cases where letters occur with the same frequency, any or all of the characters may be returned. 
*Non-trivial is defined in this case to be a character that contributes to the functionality of the program.   If the character can be removed without influencing how the program runs, it is a trivial character. 
Scoring
Score is determined as follows:
$$(\frac{n_{char}}{n_{total}}) * 100(\%) $$
With nchar being the number of occurrences of the most frequent character in the input, and ntotal being the total number of non-trivial characters in the input.   With this scoring criteria, all scores should be within the range \$[0,100]\$
Highest scoring solution per language wins. 
Input
Solutions should take in any valid string as input.   A convenient method of determining the most occurrent character in the program itself would be to use the program's source code as input to the program itself.   The program does not have to check for non-trivial characters, as they should not be included in the program source. 
Output
A single character with the highest percentage occurrence.   Each solution should be capable of outputting standard ASCII, as well as the language's codepage (if applicable). 
Errata
Creative solutions are encouraged.   Boring solutions with long padded strings substituted in for numbers are discouraged.   Standard loopholes are disallowed. 
Examples
Program:
aabbbc
Output:
b

Program:
aabb
Output:
a or b or ab

Sandbox Link

A:

05AB1E, 99.999999999999999957%
1111111111111111111 ... (9352835025086960662 1's total) ... 11111g₅B.V

g gets the length of the large integer literal.  Obviously this is too long for TIO, so try a version using 9352835025086960662 instead of the equivalent 1111...1111g.

A:

JavaScript (Node.js), 55.85% (or much more)
s=>eval(Buffer((g=n=>n?[+[n&127n],...g(n>>7n)]:[])(0b1001111010011001001100101001101110111000110111101100111110110111101111011110111011010111010011000001111111101101011110001010011011101110001110110111101111111111001011010111101101110111000111011011110111101010000111110011110111000110101100110011101011111011101101110110111001011011111110111110110101001010100010111101011011010111101111011101111011110111011010101000110010111000111100001110110011100001100101111001001011101110011n))+'')

Try it online! 
This is a 'fair' version, in that only the payload binary data is included (7 bits per character).  But the score could be made arbitrary large by padding each encoded character with as many zeros as desired.  They would still be 'non-trivial' as per the challenge rule, as removing any of them would break the decoding. 
The binary string is decoded as:
s.replace(m=o=/[^(){}[\]]/g,c=>(o[c]=-~o[c])<m?0:m=o[O=c])&&O

A:

PHP, 75%
foreach(count_chars($argn)as$c)$o[]=$c*'1111111111111111111111111111111111111111001111111111111111111111111111111111111111111111111010111111111111111111111111111110101111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111'[$i++];arsort($o);echo chr(key($o));

Try it online! 
Ungolfed:
// table of valid input chars - ASCII 0-255
// index is the ASCII number, and 1 or 0 if it is valid
$valid_chars = '1111111111111111111111111111111111111111001111111111111111111111111111111111111111111111111010111111111111111111111111111110101111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111';

// get input string and aggregate count of each letter
$counted_chars = count_chars( $argn );

// iterate through each 
foreach( $counted_chars as $ascii => $count ) {
    // multiply count by either 1 if valid or 0 if not
    $out[] = $count * $valid_chars[ $ascii ];
}

// sort resulting list descending
arsort( $out );

// display the ASCII value of the "most popular" valid char
echo chr( key( $out ) );

Counts the frequency of each character and uses a lookup table to to determine if a given character is excluded (example: ()[]{}) from being counted.   Sorts by frequency and returns the "most important" remaining char. 
Note: PHP's count_chars() only counts ASCII chars 0-255 which corresponds to the array of valid chars, so is not arbitrarily or unnecessarily long.   Using a lookup table of flags to test the validity of a result is, while not the most efficient in this case, a valid and commonly-used programming practice.