Create a new empty file in Finder called untitled.txt. If this file name already exists, name it as untitled 2.txt, untitled 3.txt, and so on.

New Empty File.applescript

tell application "Finder"
    set currentFolder to (the target of the front window) as alias
    set baseName to "untitled"
    set extension to ".txt"
    set fileName to baseName & extension 
    set maxNumber to 100  
    set counter to 1  
    repeat
        if not (exists file fileName of currentFolder) then
            set newFile to make new file at currentFolder as alias with properties {name: fileName}
            select newFile
            exit repeat
        else
            set counter to counter + 1
            if counter > maxNumber then
                display alert "Maximum naming limit reached" buttons {"OK"}  
                exit repeat
            end if
            set fileName to baseName & " " & counter & extension
        end if
    end repeat
end tell