Zarya - I don't understand how to play this one at all. The random character event keeps giving me Zarya!
She is tricky to figure out at first, but once you understand her mechanics, she is a great hero. So you have a few abilities
1) Your gun. Left click is the particle beam. Although it is a beam, it is only single target (closest target). Rclick fires the energy ball things that have an arc fire trajectory. These do AOE damage and take multiple ammo usages per shot.
2) Self shield. This creates a barrier on yourself that absorbs all damage for the duration. It only lasts about 1 seconds.
3) Ally shield. You can cast barrier on an ally that absorbs all damage for the duration. It only lasts about 1 - 2 seconds. 10s CD I believe?
4) Ult. Basically Engima's blackhole in DOTA. Sucks all enemy heroes towards the center of the blackhole for the duration. You want to combo your rightclick with this, since you damage everyone in the blackhole AOE. High energy rclick is best to make the most of this. Keep in mind: Blackhole DOES NOT disable people, so they can still use abilities, including Reinhardt shield.
So Zarya basics. When you play her, you'll notice a number below your target reticle. That is her energy level. When you respawn or just start off, it is 0 at default. The highest it can go is 100. Higher energy = higher damage. Energy building and management is what Zarya is all about. At high energy, you do insane damage, so your goal is to always try to get your energy way up so you became a massive damage dealer.
But how to build energy? Your barriers. Basically, any damage your barriers take will translate into energy. The barrier has to take the damage. So if you bubble a Reinhardt using a shield himself and his sheild eats all the damage, then your bubble gets no energy generation. So if a Hanzo ults and you pop your barrier and sit in the ult for a second, you'll get some energy. Bastion shooting? Energy. Just keep in mind your barrier has a VERY small uptime and a decent cooldown (8-10 seconds depending on barrier used), so you need to get good at choosing when to pop the barrier. Ideally, you want to use it when you know the enemy will be doing lots of damage to you or whoever they are trying to kill on your team (Phara using ult, people targeting Mercy, frontline DPS, people getting ganged).
One thing to note is the energy generation is capped per barrier usage. So if you pop your barrier with 0 energy and eat a Junkrat tire explosion, you'll probably only generate 50 energy. Same if you shield a teammate who eats a tire explosion. But combine both and you get into the high energy state.
Zarya ult is also the ultimate combo machine if you coordinate. Using your ult, then another teammate using their ult (high noon, justice rains from above, tire, blizzard, tactical visor, hanzo dragon), will guarantee in most cases that you'll murder everyone caught in the blackhole, since they are all clustered. My recommendation vs. a Reinhardt is to make sure his shield is dead or he is dead before you use it near him, otherwise he can shield block all the damage you or your team tries to inflict. Your ult is also eaten by Dva defense matrix, so don't use it when she pops that.