Most of the items that I have took me a lot of work to get, so I will make a top 10 list.
10. The North Pole. I got it after a few frost moons. But when I got it, it was godly, and it felt good.
9. The Coin gun. Believe it or not, this didn't take to much effort. I have 2 coin guns, and I just got them at random.
8. The Scourge of the Corrupter. This took a lot of Demize key mold farming, until I gave up and made an actual farm in the underground corruption.
7. The Shadowbeam Staff. This took hours of farming, until I realized how crappy it was.
6. The Horseman's Blade. This took a little while, and I died a lot.
5. The Piranha Gun. After I got the first key mold, I got about four more. But it was awesome to get!
4. The Death Sickle. It took about 5-6 eclipses to get it.
3. The Terra Blade. Although it only took me 3 eclipses, It was super hard to get.
2. The Paladin's Hammer. This took nearly 10 hours of farming, and I felt so happy when I got it.
1. The Axe. One day, I was hopping through the jungle, trying to get jungle grass seeds, and I found a Plantera bulb. I broke it, fought her, and BOOM! The Axe! I had probably fought her 150+ times with a 99% success rate of killing, and had wanted it for MONTHS. I was hyperventilating after I got it.
And Believe it or not, these are just the weapons!!!