I recently found this exploit and i know very few who know about it.
The Giran Harbor is almost always deserted other than a few passerbys. It's also not apparent what it's bug is unless you train a few mobs down there.
If go the harbor and run exactly North East you will come across a hill with a large gathering of delu lizardman warriors(lv30) and a boss/chief (lv38~). Just peg one with an arrow or spell and run back down the the to the east wall of the harbor facing the water and run up the stairs and it will trap them.
Other than getting stuck in that one corner, which doesn't always work if you can't run too fast. The mobs will also trap on the NE wall on the harbor.
Should something happen and you run low on MP or arrows, if done correctly you can use melee attack. I've only tested this with swords but should work with any melee. I've found it works when you are in a diagonal posistion to the mob.
Now the best thing about this bug is you will not need to continually grab and pull mobs. The lizardman chief if left alive will contiuosly spawn two lizardman warriors.
They might spawn on your side of the wall, if so, I've seen the best way to use this is one other person or a friend. Have a friend aggro it and have them run out and train it to the other side of wall, when there you can powershot or cast some large damage spell and make it come after you.
I've done this with a friend and solo for more than a week now and have leveled six times and gathered many adena. I have not been banned or reported(yet). The drops aren't spectacular, but the lizardmen drop mithril boots design a lot which is worth about 1k I think.