A post by Fingeek set me thinking about the worst presents you could give an ex who was getting married. Not that I would ever give an ex of mine anything but cheap flowers, of course. But hey, it's the thought that counts:
World's Worst  things to give an ex-girlfriend  on her wedding:
1. A rare, collector's edition of The Taming of the Shrew (with a note to the groom saying: "They're only a few of these left, you know")
2. A baby boa constrictor (with a note saying: "Sure, it looks innocent now, but give it a few years and it'll coil itself around you and slowly crush the life out of you. Enjoy your marriage, btw.")
3. The complete works of Thomas Hardy (with a note saying: "For those long, tedious winter evenings. You'll need it!")
4. A lifetime subscription to Playboy (with a note saying: "For those long, tedious winter evenings. He'll need it!")
5. 42 yards of bubble wrap folded neatly together (with a note saying: "sooner or later, they all burst") 
6. A 6 foot by 3 foot print of the right panel of Heironymus Bosch's triptych The Last Judgement
(with a note saying: "Thinking of you")
7. The Fully illustrated Guide to Rock, Paper, Scissors for Two (with a note saying: "I was going to get you the Kamasutra, but then I thought: hey! let's be realistic")
8. A mantelpiece decoration consisting of two doves against a blue and gold background with the legend: "Two Lovebirds built this nest" (Wodehouse rocks!)
9. Ten yards of rich maroon drapes (with a note saying: "It's curtains for you!" by way of explanation)
10. A life-sized cardboard cut-out of Donald Trump (with a note saying: "Just to get you in the mood")
In the interest of fairness, though, I should say that I personally think being invited to an ex's wedding is one of the top 5 life-events: right after graduation, the first time you have sex, your first tax audit, immigration and your first car accident (I know that's five right there - but two, three and five are pretty much the same thing) . I wouldn't miss it for the world. No, wait, that's an overstatement. For the world I might. How about - I wouldn't miss it for three tooth extractions and Fox News. Yes, that's about right.
 Not really the nastiest, of course - if you want to get really nasty you should give a can of anti-freeze with the correct ignition temperature highlighted on the side.
 I say ex-girlfriend, but you could easily use these for ex-boyfriends as well. Well, maybe not the Taming of the Shrew. Or Playboy. But all the others.
 Don't forget to insist that they 'unwrap' it then and there.
 I'm not including birth (which is one of those experiences that's over before you even know it happened, and is not something you really want to remember too vividly - kind of like Yanni's career as a musician) and death (which isn't strictly speaking a 'life' experience, is it?)