Regarding your question in the Daimond and Pearl shiny thread:
If you encounter a shiny Giratina and you kill of run from it you will never be able to encounter that Giratina again, regardless on whether it is shiny or not. You will have to catch it on the spot. Same goes for any intractable legendary.
If you encounter a shiny Giratina and you kill of run from it you will never be able to encounter that Giratina again, regardless on whether it is shiny or not. You will have to catch it on the spot. Same goes for any intractable legendary.