Packrat.

My son knows every item he ever obtained, in what manner he obtained it, and from whom the item was obtained.
He keeps a mental Rolodex of each item. A running inventory. If I remove any item from his bedroom in an attempt to sneakily rid our home of a very broken or problematic toy, it becomes the topic of discussion for days - until he finally realizes that his evil mother has thrown something away that was precious to him. Then we go through the grief process.
It is wonderful. ;}

As I write this at a little after 10:30pm on a Saturday night, he is choking back tears because I told him we were going to have to go through his toys and get rid of all the "trash."
He literally scours the bottoms of our trash cans looking for things to recycle. I know recycling is a good habit and he should be commended for his dedication to the task, but his understanding of recycling and what it truly is are two different things.
He wants to keep the empty milk jug forever because 'there must be some use for it.'
He has no intention of ever parting with any of his coveted trash.
We are beginning to have a bug problem. Ewww.

I am afraid he has inherited a genetic propensity towards being a pack rat - from my husband's side, of course... :0
And I am on the other end of the spectrum. I do not lack sentimental appreciation for truly meaningful things. I still have the shrivelled up umbilical stumps from my kids - I know, that's gross - but I do. I am sentimental enough, just not on the level that my son is.
He makes me crazy because telling him that any part of his lifelong collection is trash and needs to go breaks his heart. He is literally verklemmt at just the mention of getting rid of anything.

So please - savings bonds from now until forevermore.
At this rate, I'll be renting several storage buildings for his things by the ripe old age of 10.

And yes, he's still weeping even now because he knows that tomorrow I will enter his room with a trash bag and it will leave filled up with his 'precious belongings.' Poor baby.