I personally will use anything in my ******* to destroy you in both a duel or PvP, and I expect the same in return. I have been called a cheater for blasting an opponent with a Bomb in a duel. Well I am an engineer, so expect to eat on bombs, shrink rays, net cannons, discombobulator rays, or whatever I have on me.
As an example I started a new rogue character and decided to take up engineering with this character as well. Having a high lvl main with lots of cash makes starting over pretty easy. So i was armed much better than the first time i began. I also mailed my new rogue enough to max out his engineering. So at lvl 14 i was at 165 engineering (gnome bonus). One afternoon I log on and I am in westfall trying to cook some boar at the little campfire when a lvl 19 rogue decked out in full defias gear with twin swords from Vancleef interrupts my cooking by challenging me to a duel without asking first.
I am lvl 15, 4 lvls below this joker who is geared to the max, but for some reason this guy annoyed me. So I accepted. As the counter counted down he stealthed to try and ambush me. Instead of stealthing in return I popped out an Exploding sheep before combat. A really nice thing about Exploding sheep is that they are a lvl 30 guardian. So the sheep had 11 lvls on this rogue. As soon as combat began and he became hostile the sheep charged and blew up in his face. This knocked him straight out of stealth. The guy must have never seen those before, cuz he just stood there asking me what the hell that was. But I was busy trying to beat the snot out of him. After a second he decided to fight back. Then I tossed Big-Bronze bomb in his face and managed to win the fight, although not by much.
He then proceeded to label me a cheater for utilizing my engineering skills against him. There was honestly no way I would have lasted more than 8 seconds against him without my tricks, and the battle still did not take more than 15 secs.
Personally, I say use everything you have in the course of a duel. If you think that potions are cheap, then you would have to ban all trade-skill items to be fair. That includes bombs, engineering trinkets, sharpening/weight stones, weapon chains, shield spikes, armor kits, the cool blacksmith trinket, potions, and lets not forget enchants.
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Tastes like chicken only - not..