WordNet (r) 3.0 (2006):

strong point
    n 1: an asset of special worth or utility; "cooking is his
         forte" [syn: forte, strong suit, long suit, metier,
         specialty, speciality, strong point, strength]
         [ant: weak point]

Moby Thesaurus II by Grady Ward, 1.0:

91 Moby Thesaurus words for "strong point":
   ability, acropolis, area, bag, bastion, beachhead, blockhouse,
   bridgehead, bump, bunker, caliber, capability, capacity, castle,
   citadel, cogency, cup of tea, donjon, dower, dowry, endowment,
   equipment, faculty, fasthold, fastness, field, flair, fort, forte,
   fortress, garrison, garrison house, genius, gift, good reason,
   good reasoning, hold, instinct, ironclad reasoning, keep,
   knockdown argument, line, long suit, main interest, makings,
   manner, martello, martello tower, metier, mote, motte,
   natural endowment, natural gift, parts, peel, peel tower,
   pet subject, pillbox, post, potential, power, powers, pursuit,
   qualification, rath, right thinking, safehold, sound evidence,
   sound reasoning, specialism, speciality, specialization, specialty,
   strong argument, strong flair, stronghold, style, talent, talents,
   technicality, the goods, the stuff, thing, tower,
   tower of strength, type, vocation, ward, way, weakness,
   what it takes