I like to say: "I'll bet that hurt," or "How long have you been saving that?"
How about, 'thank you'?
In the UK we don't usually get the 'god' part, just the 'bless you' part. I tend to say 'science' when I or someone else sneezes.
On the rare occasions that someone does say the 'god' part, and if I'm feeling playful, I'll say, 'ramen brother/sister, have you been touched by his noodly appendage too?'