So... I was trying A plant's challenges, and I realized that I had some challenges that I had made up for myself a while back, so I decided to post them. Some are on the userboxes on my page.
1. Beat Column Like You See 'Em without Jalapenos or roof cleaners.
2. Beat Bobsled Bonanza without Spikeweed or Jalapenos.
3. Beat Seeing Stars with no other offensive plants than Starfruit.
4. Beat all levels in Ancient Egypt without any Sunflowers (or Twin Sunflowers!).
5. Beat Pirate Seas Last Stand 2 with only one type of plant.
6. Beat Pirate Seas Last Stand 3 with only five plants, all the the same type.
7. Reach 100 flags in Last Stand Endless.
I will post more when I come up with more!