Volibear/Strategy

Skill usage

 * is a great way of baiting enemies to overcommit in a fight to kill you. It allows a huge amount of healing in a short amount of time.
 * also gives a stack of . If you're at two stacks, use to throw the enemy behind you and go in for the kill with.
 * Flinging an enemy with and then activating  makes it difficult for enemies to run from you, giving you an opportunity to drop their health down with normal attacks and finish them off with.

Build usage

 * synergizes very well with your passive allowing you to heal a lot more over the duration.
 * Since only two of his skills are AP-based, is free to diversify into tankier items.
 * The base damage on is high enough that building attack speed is better and cheaper than AP if you want to maximize damage for that skill. Doubling the damage would take 250 AP at rank 1, and 516 AP at rank 3; An increase 100% AS only takes two items, and far less gold.
 * is thus preferable over for slowing enemies.

Countering

 * him when he is low on health to reduce the effect of his passive, thus making it an easier kill.
 * greatly depends on having high amounts of health to add damage to his . Items such as, and  are great counters, as their damage is based on the target's maximum health.

Champion spotlight
http://www.youtube.com/watch?v=pVrWNNnhSww