There is a bewildering array of close combat weapons ranging from simple clubs and axes to hand flamers and chainswords. These weapons confer no bonus to the strength or hitting power of combatants. However, as a model with a weapon in each hand gains an additional attack against an enemy in base-to-base contact, swords and pistols (or similar hand weapons) remain a useful combination for hand-to-hand fighting.
Close Combat Weapons
Source: Core Rulebook 3E, p. 66
Ordinary close combat weapons like chainswords, axes and pistols give no bonus to Strength, but pairing one in each hand still earns an extra Attack.