Have you ever think about Critical Effects. Similar to On-hit Effects, however, CE only happen when the champion deals a critical hit. As it is rarely happen, the effect should be effeciently good but also have cooldown (very OP when used on champions like Ashe and Yasuo). Let's start with the first item.
Sword of the Divine
return to League of Legend with a little rework. Its active become its passive, increase attack speed for a limited of time.
Build from:+ + 400 Gold (Total:2300 Gold)
Stats: +25% Attack Speed; +15% Critical Strike
Unique Passive: Basic attacks deal an additional 10 physical damage on hit. This changed to 15% AD during Rush.
Unique Passive: Rush: Whenever you critical hit, you gains 50% Attack Speed for 2 second. 10 second cooldown.
So basically, your base stat is not very good, similar to the old Sword of the Divine (its attack speed is less than the Bow). However, once you crit, you gains 75%, which gives you a large advantage.
This item gives you low crit chance, so it is very hard to proc Rush. This item only fit if your champ has high attack speed or high crit chance or combo with other crit items.
Build from:+ + 553 Gold (Total: 2620 Gold)
Stats: +25% Critical Strike; +10% Cooldown Reduction +35 Attack Damage.
Unique Passive: Your attacks ignore 15 Armor, crit attacks ignore 40 Armor.
- Note: Abilities no longer ignore Armor.
This Passive make every crit attack becoms very painful, specially on squishy target. Assasin may use this, for example: Shaco.
Build from:+ + 200 Gold (Total: 800 Gold).
Stats: +35 Armor
Unique Passive: You takes 25% less damage from critical hits.
Build from: Valor Shield + Chain Vest + 650 Gold (Total: 2200 Gold)
Stats: +80 Armor
Unique Passive: You takes 25% less damage from critical hits. If Valor reach 10 Stack, you takes 40% less damage from all attacks.
Unique Passive: Valor: You gains +3 Armor every second while in combat, stacking up to 10 times.