Rhyncholaelia (Brassavola formerly) digbyana has a delightful, strong citrus smell. It's quite powerful and very pleasant. A lot of hybrids of digbyana will also have this scent, especially ones which have digbyana in the recent background of the hybrid. In fact I think digbyana is where the plant I mentioned before, RLC George King 'Serendipity', gets its citrus undertones. George King is 11.72% digbyana.