Went to a 90th party on Saturday in the parish where I served as a curate. During the catching-up-with-the-last-14-years chat, I was reminded that I once did a conditional baptism (page 279 of the Alternative Service Book 1980). The person involved had no means of ascertaining whether they had been baptised as a baby, so we did a conditional baptism before they were confirmed. In that parish we did 100+ baptisms per annum, but I only ever did one of those.
Another one-off was a Thanksgiving after Adoption. (p.218) Only ever did a few thanksgivings at all, although we had one for each of our kids on the first Sunday Debbie and newborn could make it to Church, leaving the baptism until we could sort out invites and parties. I recommend it it as a patterm. However, a Thanksgiving after Adoption is not something you get to do every day.
At least I haven't had to work out how to deal with a request to 'Church' a woman after childbirth (it's in the 1662 prayer book if you have no idea what I'm talking about). Don't think I could do it in good conscience, so it's probably just as well it has dropped out of use.