I've just taken delivery of some very special solid sterling silver tie pins. These have been specially made for me, so you won't see them anywhere else. The metal has a 'hammered' texture, so it is purposefully not 100% round, but rather charmingly imperfect.
I wear mine to secure my tie to my shirt, but you can equally use it through your collar to create a nice arch in the tie in somewhat of a more preppy style. Some further reading on this style here.