As a PvPvE game, you're going to encounter hostile players in Aion whether you like it or not in the long run. Naturally, as it goes for when that player meets you and cannot speak to you since each faction's text appears garbled to the other, he'll try to communicate to you in the next most effective manner: by hitting you. Of course, you could get angry and leave, that'd be rude to do when someone is trying to talk to you, so odds are that you will strike up a conversation and start hitting him in return. You two may even have a number of friends who are interested in the same topic and may want to join in. After all, aren't group discussions much more fun and insightful? Unfortunately, as it goes, people involved in the conversation may get tired of it and collapse to the ground in fatigue before disappearing. It's a shame, but if we spoke with each other forever, we'd never get anywhere. But, regardless, the talk between you and the other player will no doubt have been fun and you may go seeking new players of the opposing faction to talk to as well to see what they have to say. However, you might get tired of striking up the exact same conversation repeatedly. You can, however, avert it by steering it a different route.
Overly extended metaphor aside, there's often nothing more satisfying than killing your opponents in creative or silly ways when it comes to player versus player content in games. I'm sure you've all done it at some point or another, or have been a victim of it. Everything from pushing your opponent over a ledge as opposed to blowing them up with your rocket launcher, blasting a traffic cone into their face, or just letting the environment do the work, it all leads to good times. Aion offers the chance to perform creative and amusing deaths to your foes, all with varying levels of difficulty to pull off and circumstances to be in place.
Keep in mind that a number of these may result in diminished rewards since the opponent will take significant amounts of damage from other sources. The point of kills like these are for sheer amusement and probably won't be easy to pull off normally. But, when you do it, it's great fun. And you'll still get credited with the kill, assuming you hit the other player at least once. Also, I'm not trying to encourage use of exploits for cheap kills here. In fact, I'm not aware of any at present.
Anyway, numbered for no other reason but to number them:
#8 Fauna Reinforcements
To my knowledge, the idea of using NPC foes to do the dirty work for you is fairly common. Using NPCs that are hostile to both sides is a bit more difficult, but can be fairly amusing if you pull it off. Luring an enemy into hostile monsters can be difficult, especially if they fight at range. But having random monsters come up and chew on them, particularly elite groups, is fun and also a good tactic for escape if you get overwhelmed. The downside is, if it doesn't work, you're giving your enemies loot and EXP.
#7 The Ledge of Death
Aion has a number of steep drops that, when fallen from, result in death or at least lots of damage when you land. Aion also has a number of skills that knock opponents backwards, as well as weapons that do so sometimes on critical hits. It can be tricky to lure a foe near to one of these, but it's immensely satisfying to pull off if you get them there and whack them off the side of the cliff. In fly zones, like the Abyss, you'll probably need to also stun them or otherwise prevent their flight so they can't immediately recover. For those of you who just love to rub things in your opponent's faces, make sure to immediately /wave at them as they go tumbling to their doom.
#6 Man Overboard
Extremely hard to pull off, but tossing a foe deep in the water is a great way to take them out. If you get your opponent in the water, they won't be able to fly unless they can jump high enough to clear the surface. Knock them deeper and they'll start rapidly taking damage. Once you have them there, try rooting or sleeping them and just watch as they slowly drown... or you could be mean and speed it up by pelting them with ranged attacks too. There are also a few places where you could send a foe over a ledge and into an ocean, where they may not be able to reach shore before drowning.