Strong blade and razor sales fueled by new marketing initiatives propelled The Gillette Co. to an 18% gain in third-quarter profits, beating analysts’ estimates, according to sources.Boston-based Gillette, which makes razors and Duracell batteries, reported net income of $416 million, up from $354 million a year ago. Sales rose 11% to $2.4 billion, driven by a 17% jump in blade and razor sales to $1.03 billion. Duracell sales rose 7 % to $514 million, and profits were $106 million, or 35%....