What would an appropriate engagement gift for a man be?

When a man asks a woman to marry him, traditionally, he gives her an expensive, elaborate ring. However, nowadays, it is becoming more common for women to ask men to marry them. So, my question to fluther is this: What is an appropriate equivalent to an engagement ring for a man? Ideally, it would be something in the same approximate price range depending on the budget of the proposer and something that he would be able to have for his whole life but if you can think of something equally as appropriate that may not last for his whole life, please let me know.

So far, the only appropriate thing I can think of is nice, possibly engraved, pocket watch or maybe a nice tie pin or pair of cuff links for a man who wears suits a fair amount.

Hit me with your ideas please!