Well Squall and Seifer have both done Rinoa... Multiple times probably. But I'll abstain on the basis that I know next to nothing about Laharl and Mid-Boss other than their species and that Laharl is freaking adorable.
Ramza/Delita despite knowing next to nothing about these guys either. I know enough about Siegfried and Nightmare to know they ain't getting much, if any. Siegfried's too busy struggling with insanity and Nightmare's too busy gathering souls. Also I don't think he'd even be interested in sex unless the Soul Edge grew a vagina.