A trend that's been popular for quite some time now is the Monogram Cake Topper. Sure, there are many places to order them, but I personally suggest Toppers With Glitz. From personal experience, they do beautiful work, with quality metal being used for the actual letter.
They have many different fonts available, and any color crystal you could imagine. Sure, their pricing might seem a little steep, but they provide great products, and something that you can have displayed on a shelf or next to a framed invite for years to come!