Hm, Solo runs?
Did a Solo Dratini run in my HG. Was a pain when I got to Mahogany Town.
Did a Solo Larvesta run in White. It was more troublesome breeding the Larvesta for it than it was to run though the Gyms.
Currently doing a Solo Guy run on Unknown in Tales of the Abyss. Center has saved my life so many times. Literally.
For others...
Nuzlocked Yellow, Gold, Ruby, Pearl, HeartGold, and White.
Did a Magikarp-only run in HG, but it only started at Goldenrod. Had to keep on hatching so many Magikarps to keep abusing Flail+Sash