There are many players with different opinions on this topic. Some people resignate away from pures, while others love them. There are a variety of different types of pures. These can vary from strength (being the most common) to summon pures. Plenty of people select to be pure for either fighting(pvp), or the general fact that you are a much lower level with a specific item than most. For example, a level 40 assault runescape pure can wear a godsword.
A different type of pure is a hybrid. This is when you have generally 60 assault, 80 strength & one defence. Being hybrid means that you also train range & mage. These stats will NOT grow you a combat until you get around about in the mid 70's to the early 80's. Prayer is as well as a common stat for a pure magic to get as at level 25 you can "protect item" meaning that, while activated, you can keep one additional valuable item on you once you die. A pure is fundamentally a runescape account who focuses on only a couple of stats. Having 99 in a stat at a low level is thought about a pure. most pures try not to train defence so they do not complete quests which give them defence experience. Except if this pure were to be a tank. A tank is pure who trains defense ranged and magic.
Some common PK weapons: there are many weapons used to PK. Here is a list of the most common ones used:
Armadyl Godsword (special hits 25% more damage than normal attacks) Dragon dagger P++ (used for the KO as it uses 2 attacks at once. meaning it can slaughter those who are unprepared) granite maul (often used between levels 44-70 but some higher levels use it. Its special is a "quick attack" which will swipe 2 times again instantly provided you click the special attack bar twice. Used for quick KO's either with range to maul or blitz to maul) dragon claws (arguably the most powerful PKers weapon. Its special attack will hit 4 times which can be used to hit a damage of over 70. Sometimes the claws will "fail" meaning that they will only hit a 0-1. each special attack uses half the bar)