Crinum thaianum (better know as the Onion Plant) is quite an interesting looking species as it's one of those aquarium plants which grows a lot longer than others making it ideal for larger aquariums in which you are looking to cover up filters/heaters.
In addition (and probably no surprise) is fish tend to avoid Crinum thaianum because it doesn't taste very nice! So fish such as Severums that love to nibble on aquarium plants avoid this one like the plague which makes it popular for this very reason. When planting Crinum thaianum make sure only the bottom 1/3 of the plant is planted - I find it easiest just to literally place it where you like and then wiggle it down a little just to keep it in place. Any more than this and it will rot away.
Suitable for a wide range of conditions too, Crinum thaianum is ideal for beginners and up.