My husband picked out my engagement ring. It wasn't exactly what I was expecting, but he thought the ring was beautiful and said it reminded him of me. So I still wear that ring. We decided that when we have our vow renewal ceremony, we'll get new rings together.
One of my guy friends solved the situation in a really romantic way. He picked the date he was going to propose, and then bought a ring of that month's stone (avoided April since April's stone is diamond) and had the date he was going to propose engraved in that ring. So he called that ring the proposal ring and after she said yes, he brought her to the store and she picked out the engagement ring and he picked out the wedding rings. I thought it was really sweet.