Aside from my car, probably the £2000 2 week trip to Egypt a few years ago. It included a Nile cruise, 4 hotels in 4 cities, and 2 internal flights. Worth every penny.
I guess after that it's probably gaming consoles, though I forget how much I paid for each of my ps1, 2, 3 and psp over the years. Not to mention games for all of them.
If we're including things we collect over a long period of time then my entire 40k/Horus Heresy collection probably amounts to a fair bit. The Horus Heresy collection alone amounts to £200 over 20+ books at £8 each.
And over the last 6 months I started playing Magic; The Gathering. I must have easily spent over £1000 on cards, £200 of which is my mono-blue devotion deck.