I noticed today that i had 120GiB of data in my Mac's Trashcan. I had enough. so I tried to kill it, and discovered a nice hidden feature.
rm -fr ~/.Trash ln -s /dev/null ~/.Trash
Now, when you delete a file in Finder, you get a nice pop-up warning that the file will be permanently deleted.
### Update (Setember 25th, 2010): As it turns out, OS X defaults to this behavior whenever ~/.Trash is unwritable as a folder. If you were to place any file in ~/.Trash, you would see the same behaviour. Oh well, it's still rather useful in function.