I have had a large magnificent anemone (heteractis magnifica) in my tank for 3+ years now. It has recently split and nicely located on an easy to move out rock. The size would be approx. the size of a mans hand extended out. (9 inches x 9 inches)
I know this anemone is rare because I have yet to see it at any of the local marine specialty fish stores. It is considered one of the most difficult to keep needing almost perfect conditions but it has definitely stays strong, beautiful and healthy in my tank I am sure anyone in the hobby with good lighting and fairly good water quality can keep this.
Mine was originally that size and has grown into a football or soccer ball sized and if you have the space and you will need it this will grow and thrive equally. I am open to reasonable offers so please email me privately. I will not accept less than $1000 as I know its value having been acclimatized to captivity and tank conditions.
http://en.wikipedia.org/wiki/Heteractis_magnifica