The "Burn Everything (and sometimes Heal)" Guardian
(first of all as an FYI this is Felidae. But because Tumblr is dumb and stupid I can't submit this from my Felidae blog. Sadface :< )
ANY. EVERY. On a serious note, I've taken this "Burn Everything (and sometimes Heal)" into events and into dungeons and I've done just fine. It's not necessarily an optimal build that focuses on purely one thing, but it gives both good damage and good support, so if you're a generic "I just want to hit things and also stay alive" person then it should work.
Useful tip, build or trick:
Your virtues are important and you're a big dummy if you aren't using them. Guardians aren't actually built around their virtues, which we could consider to be odd and it means people often only pop them for their own benefit. If you're going to do that, this build is not for you (and you're a silly guardian player.)
Check your traits! You want to make sure your first virtue (Virtue of Justice, aka the one with the fist symbol) inflicts AoE blind in addition to the burning damage it gives you and others, and that it's instantly re-usable upon the death of a mob. On bosses or events when multiple mobs spawn, this is as close to a spam blind as you can get, and it also means you can practically perma-burn anything you can hit. Which is awesome.
Your shouts. I often run with Retreat for the Aegis because it means I have three blocks - my natural aegis every 40 seconds, Retreat, and then my third virtue if necessary. (Remember that your third virtue should be popped as a last resort because that takes away your 40 second aegis passive!)
Stand Your Ground is great for stability and is essential for fights like the revamped Teq fight, for instance. You can swap it out for other shouts that better suit a situation though, and the best part of Guardian shouts is they really give you a lot of choice. Save Yourselves is another really great shout that gives you a metric ton of buffs, although the "Burn Everything" Guardian really doesn't focus much on elongating buff time all that much. It can still be useful in tight spots, though. Generally, you're always going to be running with two shouts minimum, with the third utility slot being available for either another shout, or for a consecration, etc.
Burn things. All the things. Everything.
On a more serious note, this build runs on Power/Condi/Vitality stats in your armour. It gives you a nice buff to your health, it gives you a very nice buff to your condi damage because you're going to be aiming to set fire to everything you can hit, and it also gives you some decent power so that you can still do damage even if you aren't setting fire to things.
I personally elect to run Greatsword/Staff because the Greatsword has very nice utility in and of itself, with one leap and one pull, along with a symbol that pops retaliation. Staff is often there for when you need to play support, and believe me that it works. I've been accused of thinking poorly about my build and then choosing to run staff considering that staff is about healing more than anything else, but the fact of the matter is that if you're running with teams that know how to play, you don't need to be giving them 6k heals on your Empower. At level 80 and not with any Ascended gear, I can heal for 2.5-3.5k per Empower on the staff, and the staff's orb can also give small boosts in the heals when it passes through somebody, and/or when you explode it. (This does mean that to be effective if you are supporting, you need to make sure you're positioned to get the most out of your staff.)
On any event or boss when mobs spawn, you want to make sure that you hit them. Virtue of Justice mass blinds and gives everybody burning, but namely, it gives you burning. Which is good, because you're built to burn things. If you trait accordingly so that your virtue recharges every time a monster dies, then in hectic fights with lots of mobs, you'll find yourself spamming it a lot (and you should spam it as soon as it's available because the blind is more useful than you think!)
Remember that your virtues aren't there for you, they're there for everybody else in your party. Sure, you could save your second virtue's regen for when you need it most, but what happens if two of your party is dead because you decided to hog it until only you needed it rather than popping it when people started to get low? The clue that your virtues are not for you is that they are all AoEs. It does mean that sometimes you have to pop your third virtue for the sake of your party and you end up taking hits you could have avoided, which can be a niggle, but at the end of the day it is your job to give out shouts and virtues for your party when they need them and not when it best suits you. Spamming blind makes a shocking difference in long and drawn-out fights with lots of monsters, popping the regen keeps people in good health and gives them precious extra seconds they wouldn't have otherwise had even if you haven't statted into the likes of healing power.
Your Virtue of Justice allows you to cause burning regardless of your weapon, too, which means you should never be afraid to switch into staff. Your condi damage isn't reliant on your power stat, so your burning will always do the same decent damage across the board even if you switch to staff, Empower and then use your orb. That's why condi damage is important - you can deal constant fire damage and still be of use to your team even when you switch to support them. The power just helps when you go greatsword and wail mercilessly on monsters.
tl;dr: focus on your team before yourself because you've statted to make sure you can always output decent damage per burning tick regardless of your weapon. Pop your shouts and virtues at an apt time when your entire party needs them and remember you bring more utility to the table than a toolkit on steroids - provided you play your class right.
And sometimes hit things with your sword/mace/weapon of choice.
