For me, it would have to be surface mail. I have sent surface mail presents stupidly early to NZ four times.
First time - worked a treat, was cheaper and arrived about a week before Christmas
Second time - post office operator labelled everything up as Airmail and tried to charge me and when I said I didn't want to pay that price he said he couldn't cancel it as they were pre-printed stamps and it all got very heated (I won. But it took over an hour to sort out, and it was a long time before I braved the post office again in case the customers lynched me!)
Third time - It all arrived just after Christmas
Fourth time - it all arrived six days after sending and my family thought I was mad
So, yes I saved money, but not sure it was worth it.
What are your stories?