[Idea] Category Tags can help everything! Here's why!
#The Idea: Tags
Category tags are addendums attached to a post to explain what general category or categories a post fits in.
For example, if I posted a post complaining about Annie support I could attach the tags "Annie", "Nerf", and "Balance". Pretty much think of how Youtube assigns tags to videos, they're arranged at the bottom and help with keyword searching as well as comparison to other videos within that tag's subject.
#The Process
###Assignment
The way I see it there are three general ways to assign the tags. All these ways have pros and cons with their specific approach.
#####1. OP Assignment
The OP chooses what tags he/she wants associated with his/her post, starting off as one vote away from activation (mentioned later). Viewers then can vote on what tags they agree with with a single click, the first +1 'activating' the tag and applying it to the post. This does however run the risk of posters putting up a single or even no tags defeating the purpose.
#####2. Default Assignment
Every tag is open for voting on a post at a default 0. This let's viewers and not the OP to choose what kind of post it is, which leads (hopefully) to a less biased and funneled decision. This may (and probably will) get incredibly cluttered however.
#####3. Visitor Assignment
Viewers come in, recommend a tag and put it up with a +1. But until one is recommended and approved by others it won't associate with the post. Imho this a bit too complicated on both sides, but it is an option.
What way do you like? Have another way?
###Voting
So here's the unique idea. Vote on the individual tags themselves! A 300+ score on a "Useful" Tag would be very popular but maybe not as popular as a post with a 100+ score "Bug" Tag within their categories. This helps alleviate the natural competition element of voting, allowing for an easier time to grab visibility within your own topic.
The front page will still be a free for all, upvote/time, 'most popular' mosh pit, but when a tag is searched you can see what more great posts having to do specifically with your topic.
###Activation
The biggest problem though is when an OP first posts, what is to stop him/her from spamming every tag? What's to stop everyone from doing that? Well a tag by itself, posted by the OP, might not have to do with the post as mentioned, but if that tag gets even one vote it is 'activated' and now the post will be associated with the tag.
The inverse can also be used. So when a tag gets enough downvotes, stating the posts irrelevance to the tag, the tag can be 'deactivated' after a point of negative score and the post will no longer be associated with that subject. This also protects against sudden post re-writes through troll edits.
###General Poros 
Tags can immediately help with ordering. What I mean by this is after searching for a tag like "Varus" you can then use Hot ordering to order all of the posts with the highest rated "Varus" tags that were posted recently. The same should hold true for multiple tag searching (like "Varus"+"Runnan's Hurricane") by simple addition provided a post has both tags active.
Tags can also allow for easy Red visibility, so Network Engineers could look for Tags like Lag, Servers or Disconnects and Game Designers could look for tags like Bug, Nerf or Buff. There are endless possibilities, as well as easy implementation (if the system is already implemented) to add or alter possible tags.
There is also the possibility of self moderation with a brilliant idea form NoxiousIce, the ability to up/downvote the tags themselves. If a tag gets below a certain threshold, similar to vBulletin comments, that tag would be deactivated and the post would no longer be associated with this. Along with upvoting to produce a 'buffer' for actually relevant posts. Most would not bother with this unless it was actually a problem, but the option is there.
Tag availability can also help with proper forum locations. For example the tags Champion Concept, Fan Art and Fan Music can only be enabled within the Fan Creations sub-comm. This would funnel relevant posts to where they need to be to get proper and constructive views, as well as deny irrelevant subjects.
The Beta platform is perfect for implementing a new system like this, as well as allowing an easy medium to brainstorm more and/or better tags for posts. As well as the ability for negative feedback about lack of certain tags and possible bad tags.
As was said by Burdlover90 here this also could be a way to replace or at at least influence the current CB upvote/downvote reputation system. For example, instead of a general upvote a viewer can upvote a specific tag, allowing a post to rise within that category but not others. Or, as another idea from the same convo, you can keep the general voting but have total tag upvotes/downvotes influence the post's weight.
###General Cons 
The first immediate problem I and more than likely many others would be worried about would be trolls and ragers spamming tags to grab attention, and there is very little a system can do to prevent this from being done, but with the above stated option to downvote and therefore 'deactivate' tags allows the community the opportunity to deny undeserved attention. Or simply by adding a "Tag Spamming" option to the current report function. There could be better solutions as well, but it's a start.
Post content will not be changed, only what Keywords are associated with it. So nothing will stop mislabeling and sudden edits. That's simply outside the scope of what tags can do.
There should not be the option to delete a downvoted and deactivated tag and re-tagging it with 0 votes. Whether this is done by lack of deletion privileges or by vote record keeping (re-tagging brings in the old vote "score") is up in the air.
No list of Tags will ever be complete, and it would be hard to allow older posts to incorporate new tags added to the system. While the Beta is still a Beta this can be somewhat overlooked, but upon release it's either dealing with a limited, non-expanding pool, or limiting the visibility capability of older posts.
#####List of Possible Tags, Feel free to suggest more
Within Site Feedback
Idea
Feedback
Bug
Within G & S
Guide
Tips
Help!
What do?
Team Comps
Strategy
[Specific Champion]
@Riot
@[Specific Rioter]
Build
[Specific Item]
Meta
Itemization
[Specific Map]
[Specific Mode (permanent)]
[Specific Mode (temporary)]
Within e-sports @[Specific pro]
[Tournament]
Question
Schedule
@Riot
@[Specific Rioter]
@[Specific Team]
[Specific Team] (About instead of @)
Recruiting
Within Live Balance
Nerf
Buff
[Specific Champion]
Vision
Map
[Specific Ability]
Counter-Play
Stealth
@Riot
@[Specific Rioter]
[Specific Item]
[Specific Summoner Spell]
Balance
Within Fan Creations
Champion Concept
[Specific Champion] skin
Fan Art-Visual
Fan Art-Audio
Video
External Site
Tool
Within Memes & Games
Meme
Game
Gifs
Funny
Link
Interactive
General Tags
Vent
Rito Please (We'll need one, we all have to admit, we need one)
Rage
Funny
Philosophical
Story
Personal Experience
Rant
Question
PSA (Public Service Announcement)
@Riot
@[Specific Rioter]
New
Insightful
Helpful
Negative Tags
These are an interesting idea. Tags that start on any new post as deactivated, but with enough (not a lot, 5 or so) votes on a negative tag a post can be associated with these categories.
Inappropriate
Hateful
Re-post/Spam
Troll
Other
If we can have a dynamic pool of tags within this system we can be more specific as well as have tags for changing terms like @[Specific pro] or [Patch x.x Feedback], as well as the opportunity for the community to request other tags like Quick! (A pre-fix I've used here) or Welp, shit or others that can be nice additions for unforeseen popular topics.
#####Credit log
---QuesoLoco
---Feedback off of an old post of mine
---NoxiousIce
---Burdlover90
---Rioter Pendragon (for starting some great conversations)
---Thunder Dreamss
#####Change Log
---Added Youtube tagging reference to help explain the idea better
---Added Burdlover90's tag suggestions along with Negative Tags
---Reworded ordering Pro section
---Added a few more tags like "Viable"
---Reworded "locking" section to simply explaining why I think deleting tags shouldn't be an available feature.
---Added more to the Process section to better clarify the system itself, please tell me if it's confusing!
---Made sure to emphasize the fact that this is a WiP post