It's weird but most of my shinies in G/S/C were poison, I still remember my first- shiny Koffing :)
I had also: Victreebell (from Bellsprout), Crobat ( one from Zubat one from Golbat), Beedrill (from Kakuna), Jumpluff (from Hoppip), Pidgeot( from Pidgey), Noctowl (from Hoothoot), Snorlax and that was very funny- I didn't want Snorlax, I just wanted his Leftovers, but I forgot to teach a Pokemon Thief, fortunately I saved before battle, when I restarted the game Snorlax was Shiny. Kinda cool :) I also had a shiny Sudowoodo and a Hypno (from Drowzee). But my favourite was Tentacruel! It looked awesome in Crystal! I always wanted shiny Skarmory, but I had'nt that much luck :/