Mystic turbans

People are stupid and lazy. I profited like 200k just by buying a lot of mystic turbans, then changing it into blue pieces of clothes and selling it for like 2x the price. This also works with red robes / red pieces of clothes.

Medicine pouches

I got one knight in Port Hope, only exping on swamp trolls, he can get like 60 medicine pouches per night. I have obtained few slug drugs so far. They go for 150k each or even more.

Dwarven pickaxe monopoly

There are few daily spawns of dwarven pickaxe around Tibia. The main advantage is that they are all on FACC. Just create an account and set them to the locations. Then, people who will need them, will have to buy them from you. I usually sell them fo 10k each.

Carniphilas, Carniphilas task

I don't think many people usually do this task, however I have done this on all of my characters. You can repeat it 3x, that means 450 carniphilas killed. I usually loot 1 carrot on a stick (which goes for 100k) and if lucky, you can get another from Deathbine (Carniphila's boss). Deathbine also drops sweet smelling bait, which goes for 200k aprox.

Fist on a stick

The only way to obtain one is by killing these new creatures in new tomb. None really hunts there, so feel free to supply your server with expensive camel mounts!