Being a melee character, a rogue is heavily dependant on items for maximum effectiveness. If you’re naked (not that you should be) you can’t use any offensive skill, so you’re pretty much stuck to auto attack with your fists. A mage could get by, but melees are toast. Obviously the most important item you will have is your weapon. Through your life as a solo rogue you will be taking damage but in groups you shouldn’t be. So armor, even though important, is second to weapons.
That being said, World of Warcraft is a game where rogue useable weapons are few and far between. Quite honestly, it has been my experience to find 2-handed weapons in abundance and rarely a sword. Daggers are practically unheard of unless it’s from a quest or specific creature kills. Fist weapons are even rarer. I will first go over the details of weapon selection, as it is the most defining characteristic of a rogue.
Daggers Vs. Other Weapon Types
The first and most important thing to consider when selecting your weapon is that Ambush, Backstab and Mutilate are only available if you have a dagger in the main hand (Mutilate requires 2 daggers). If you don’t have a dagger in the main hand, those skills become unusable. I will list the pros and cons of weapons below.

It’s easy to see that daggers are the best choice for consistent damage since they attack more often. Swords and maces attack at a slower rate and hit less often, making damage more sporadic. So why do people opt away from daggers then? Sinister Strike is why. This skill has its own timer, so weapon speed means nothing while weapon damage means everything. For example, let’s say you have a dagger that hits for 120 damage every 1.5 secs and a sword that hits for 250 damage every 3 secs. They both have the same DPS so in a perfect world, just counting auto-attack damage, they should be the same. Factor in Sinister Strike (at max, it does +98 weapon damage) and you’re looking at 218 damage with the dagger and 348 damage with the sword. Nearly a 40% difference in damage and that’s just considering base damage, not the bonus you get from attack power, enchantments and critical hits. All of this is completely independent of weapon speed. Backstab, Mutilate and Ambush are the reasons you would use Daggers. Ambush can only be used once a fight and once you’re 70 and do the high level content, you’ll find you’re using Ambush about once every 3-5 minutes. You cannot use Backstab or Mutilate when fighting alone with any degree of ease as you need to be behind your target. In a PvP battle, you won’t often get a chance to use either of these skills. Some of the high level content doesn’t allow you to position yourself behind the targets. The simplest reason however is that in the majority of the combat situations, you will be using Sinister Strike a lot more than Ambush or Backstab and you should focus on making that skill do as much damage as possible. You can compare the numbers, if you wish, with the formulas in Section 2.1.2.
All that being said in favor of swords/maces/fists, it’s important to remember than daggers are faster and give access to Ambush/Backstab/Mutilate. That means that daggers, in general, will apply poison twice as often as swords will (based solely on auto-attack), which increases your DPS by at least 10% when you initially reach 70. Backstab and Mutilate are amazing tools in groups as you will generally have the target’s backside available to you. If you’ve opted to get Mutilate, then you would need to consider aggro a bit more but the skill truly shines when in a group.
Another factor to consider is that swords and maces are a lot more common than daggers. You will still find daggers but more so in instances and quests. I highly suggest

you try both fighting styles out to see which you like more. Just know that damage-wise against “normal” creatures, swords are the most powerful.
If you were to categorize the weapons based on your playstyle, I would say swords/maces/fists work best for PvP. Daggers work well in a group PvE setting. Swords/Maces/Fists work well with a Combat build for PvE raid instances.