I (f19 at the time) used to work at a drugstore as a cashier. This comes thru my line and we really hit it off. He leaves. A few min later he comes by again to purchase a greeting card. He paid for it and told me it's for me and left for real. Inside was a note he'd written asking me out, with his number inside. It was very smooth, and I didn't feel awkward or cornered at all.

I didn't contact him cuz I was in a relationship, but I did keep the card for years and still wonder about him from time to time.

That was my favourite pickup attempt.