#PowerShell, 81 Bytes

(-join($args[0].Split(" ")|?{$_-notmatch"^(and|or|by|of)$"}|%{$_[0]})).ToUpper()

Explanation

Split on the spaces creating an array. Drop the offending members. Pull the first character and join together. Use ToUpper() on the resulting string.

PowerShell, 81 Bytes

(-join($args[0].Split(" ")|?{$_-notmatch"^(and|or|by|of)$"}|%{$_[0]})).ToUpper()

Explanation

Split on the spaces creating an array. Drop the offending members. Pull the first character and join together. Use ToUpper() on the resulting string.

#PowerShell, 77 Bytes

(-join($args[0].Split(" ")|?{!($_-match"and|or|by|of")}|%{$_[0]})).ToUpper()

Explanation

Split on the spaces creating an array. Drop the offending members. Pull the first character and join together. Use ToUpper() on the resulting string.

#PowerShell, 81 Bytes

(-join($args[0].Split(" ")|?{$_-notmatch"^(and|or|by|of)$"}|%{$_[0]})).ToUpper()

Explanation

Split on the spaces creating an array. Drop the offending members. Pull the first character and join together. Use ToUpper() on the resulting string.

#PowerShell, 81 Bytes

(-join($args[0].Split(" ")|?{$_-notmatch"^(and|or|by|of)$"}|%{$_[0]})).ToUpper()

Explanation

Split on the spaces creating an array. Drop the offending members. Pull the first character and join together. Use ToUpper() on the resulting string.

#PowerShell, 77 Bytes

(-join($args[0].Split(" ")|?{!($_-match"and|or|by|of")}|%{$_[0]})).ToUpper()

Explanation

Split on the spaces creating an array. Drop the offending members. Pull the first character and join together. Use ToUpper() on the resulting string.