User blog comment:TheTobarMethod/So...Tri-Force Vayne lol?/@comment-4593717-20130303194812

Build Trinity Force on Vayne if you're going Assasin-style. Here, I'll copy+paste something I said earlier:

 ...BT and IE give more offensive power, but not for bursting, which you might consider if building Vayne Assasin-style (which I highly recommend because ganking mid and bursting down the enemy mid with your APC (supposing you have one) is a really nice way to get Vayne the snowballing she needs to become a monster and basically single-handedly win the game for your team.