The Death Company is easily one of the most dreaded assault units in the game. They can be anywhere from two to ten men strong, but 8 or 10 is the most formidable.
They can use Jump Packs, a Rhino or a Drop Pod (or, if you buy it as its own slot, they could always load up into a Crusader), but Jump Packs are the most common choice. And they're almost always accompanied by a Chaplain (usually Lemartes)
So what makes them so scary?
Base 2 attacks (not including +1 for BP & CCW), full Space Marine stats, Frag & Krak, plus Feel No Pain, Fearless, Furious Charge and Rending!
On the charge, a Death Company with Lemartes or a regular chaplain is I5, S5, A4, and reroll misses. And every reroll is one more chance to get a S5 rend.
They are a truly terrifying unit, but they do have their weaknesses.
Feel No Pain doesn't work against Instant Death or CC attacks that ignore armour (power weapons, rending attacks in CC), so S8 ordinance are one of the few shooting attacks that are worth directing against them, meanwhile high-initiative power-weapon squads like Howling Banshees are a serious threat, but other than that, there's not a lot that can stop these guys if they're used properly.
So how would you handle The Death Company (And a Chaplain)?