The Expendable. Ultra high-risk marksman
An extremely high damage marksman who gets stronger the less health has.
Passive: Last Stand---- Gains bonus attack speed = to the percentage of his missing health.
A: His auto attacks start off really close range compared to other ADCs.
Q: Precision Shot---- Consumes mana to fire a long ranged basic attack in the form of a skill shot (will not pass through minions). This ability is counted as a basic attack in every way, it can even crit. It has no damage modifier, leveling the ability reduces mana consumption and cooldown. The cooldown scales off of attack speed (shortest being 1.5 seconds I think).
W: Drones---- Summons two small drones that float above target's head (he can use it on himself or on a ally champion). Each drone deals 25% of your AD as basic attacks (they can crit), you can control what the drones target by holding down Ctrl and right clicking. Drones scale off of your attack speed. (basically you can cast it on yourself and shoot someone as your running away). Drones have the same range as you. (drones also scale off of AP, not sure how much though)
Passive: Accuracy---- Auto attack range is increased with every level put into this ability.
E: Forcefield--- Creates a forcefield that scales off of AD and AP protecting you from damage for the duration of the ability. The duration and is reset anytime you get a kill or assist. (health regen effects are also delayed until 2 second after shield is gone; but will return instantly. So if you have lifesteal it will build up as an instant heal but you can get killed before it takes effect...)
R: Detonate---- Fires an explosive shell stunning target and those around it. This ability scales off of AD and AP, and increases in damage for every percent of your missing health (sort of a reverse riven).
Self Detonate---- Target yourself (has a slightly delayed charge), causing you to suicide bomb in a larger radius instantly reducing your health to 1. Damage scaling is the same as the above, but counts as 100% of missing health.
Furor boots and triforce are probably his absolute most core items. Guinsoo's Rageblade is another idea, though I am not sure how the numbers would work out to make it worth the buy.