For implement users who take the Superior Implement Training feat in PHB3, there are several superior implement properties (on page 195) that can increase attack bonuses. It requires you to take a feat (Superior Implement Training which lets you use one type of superior implement) and the materials cost (slightly) more than the standard object.
There is the Accurate property, for example, on the Accurate Rod and Accurate Orb:
Accurate: You gain a +1 bonus to
attack rolls made with an accurate
For implements users who have a number of powers attacking the same defense (Ref, Will, or Fort), there are also properties like the Undeniable property:
Undeniable: You gain a +1 bonus to
attack rolls against Will when
attacking with an undeniable
(There is also Unerring for Ref and Unstoppable for Fort.)
These three properties are often paired up with another, as in the superior implement Crystal Orb:
Name gp wt properties
Crystal orb 27 2 Energized (psychic), undeniable
where Energized(psychic) increases the damage of powers with the psychic keyword.