Utilizing Kor'sarro

Kor'sarro Khan is, by far, the weakest special character in Codex: Space Marines. Vulkan gives direct offensive benefits to all your thunderhammers, melta- weapons and flamers. Lysander is an offensive monster that buffs your army's ability to hold its ground (which can be a drawback if you're not careful). Calgar is the slayer of all things large and small, while providing the benefits normally only gained by an inquisitor lord to your squads. Even Tigurius helps out with eclectic armies that need to make coordinated strikes (not to mention that he can pull some amazing stuff out of his bag of psychic tricks). Shrike turns your marines into a speedy assault force.

...but what does Kor'sarro Khan do? He gets some special equipment and rules for himself, all he does is allow your more mobile units to outflank. So let's analyze this in its entirety.

1) He and his squad have furious charge. This is great for Khan joining a unit of assault terminators if he's on foot, or perhaps a bike-mounted command squad with power weapons. It's also nice for any other characters that want to join up with that unit like a chaplain or librarian. Take the chaplain for maximum carnage, or take the librarian for precision strikes. Nothing says 'kill' like an I5 epistolary with S7.

2) He and his squad have hit-and-run. While the effectiveness of the bonuses conferred by this ability are debatable, there are ways to turn up the dial on its power level. The main reason to use hit-and-run is to either a) escape from an undesirable combat or b) make a mildly effective charge to block your unit from being shot during your opponent's next shooting phase. So if you're using high-cost, large, resilient units that aren't very effective in close combat but are decent at dishing out the firepower, then go for it. Use the largest unit of bikes possible, led by a power weapon-wielding veteran sergeant and the Khan... or else a large unit of foot-slogging shooty terminators.

3) Moondrakken is just a bike. The only reason to use it is if you want to use the Khan to lead up a fast-moving unit that's not vehicle mounted (assault squad, bikes). If you feel the need for the Khan to leave his unit and attack a vehicle on his own or assault a small vulnerable artillery team, then he may want to leave his unit, running during the shooting phase and then charging. This just seems like a helpful option that will never see substantial use because of the subsequent vulnerable situation in which you leave the Khan after he does his damage.

4) Moonfang is a nice gem that makes the Khan just a little more tempting. While the ability to cause instant death is nice, there are tons of characters (as well as the entire Daemon army) that are immune to it. Considering that the Khan only has five attacks on the turn he charges and causes instant death only on a to-wound roll of six, it would seem beneficial to attach a chaplain to help raise the possibility that he'll hit that one six.

5) Anyone who's played an objective-based game against an army with a hefty amount of scoring units (or just a high quantity of units in general) knows that it's an uphill battle. Using bikes as scoring troop units gives you the versatility of having fast-moving anti-everything units turbo-boosting their way towards controlling or contesting objectives in the late game. It becomes much easier to manage your units' movements when you have a large web of redundancy in your usually non-scoring units to back up your objective-capturing plans.

6) Outflanking has always been and will always be a mixed bag; honestly it's just an empty bag if you ask me. Against a good player with a versatile force and the ability to mass firepower it's just a bad bet because you're dialing down your army's efficiency to take a chance at increasing that efficiency at some later point in the game. What this does is make your opponent's decision making easier. He has fewer targets and more flexibility in his target selection process. But I digress. If you're going to use the Khan's abilities, then it's best to keep this one as an option against an opponent who has decided to use similar options. Try keeping one unit in reserve; this is preferably a bike squad that can minimize the impact of having it show up on the wrong side of the table by turbo-boosting. It's probably a good idea to use this unit in an army where the Khan is on a bike and riding with a biker command squad; the remainder of your force should be fast-moving as well so that you can put pressure on one half of your opponent's force right out of the gate. This way, when your reserve bikers show up, they can either a) press the existing advantage you have in sub-dividing your opponent's army, or b) have a unit in their backfield that's there to finish what the rest of your army started (or tie things up until your main force can bridge the gap).