The TileMax bit from ForgeFix has an asymmetric design and precision tip to cut resistance levels by 25% and prevent the bit 'wandering' while in use. This reduces the likelihood of tiles cracking or chipping when drilled.
TileMax bits are diamond ground and made from tungsten. They are so hard, says the company, that not only will they drill most tile substrates, they will drill through marble, concrete, engineering brick and granite.