In Pokémon Colosseum, you can combine the control-stick neutral position glitch
with the cliff glitch
to make the process of purifying Shadow Pokémon easier.
Bulbapedia says a 'purification glitch' can also be done in Pokémon XD under different conditions. I think I remembered it being another infinite walking trick from indoors, but I don't know the specifics.
Does anyone remember? Thanks!