Old items you own that you love and use a lot....

Lol, basically almost everything.
... I have a few really old things that I treasure, but don't really use much anymore, because I don't want to wear them out.
Things like that would be my first really serious watercolor brush, a W&N series 33, no 6 (they don't make them anymore). It's so worn it's more like no 4 now, but it's still a very good brush. It's more of a mascot than a tool now. The same I could say about a couple of worn out Parker Vector fountain pens, which are actually hardly usable anymore, they're that worn. My oldest pen is still in good shape though. It's a Parker Frontier. It's also a treasured mascot. Pens that I actually use these days tend to be either $500 - $2000 items (because then I have to use them, before I die, don't I?) or cheap Chinese pens that I'm just interested in.

I have a keyring that has been around a few decades. A gift from one of my first employers. It has a small knife blade (that I keep razor sharp), screwdriver, bottle opener. It has seen, and sees, a lot of use. It's always handy to have around.

I have a great, ultra quality wallet that I've had for at least 30 years, maybe longer.

I have two big ceramic mugs, that have been around a few decades, since my student days.

A thing that come closest to what you're asking about would be my HP50G calculator. (I actually have three of them, just in case, they're not made anymore). It's been a close companion for a long time. I can't imagine life without it (before it, I had a HP49+, HP48G+ and HP28S, basically older versions of the same calculator). Though, since I don't work anymore, it hasn't seen that much use lately.

My Canon 6D camera is not terribly old, but feels like an old companion, and there is nothing new on the market that tempts me to replace it.

Boots, shoes, jeans, T-shirts, I use until they literally fall apart, if I like them and they're comfortable. If they're not, I don't wear them at all and eventually throw them away to make room in the closet.

I've had a neon green fleece jacket for about 20 years now and I still wear it even though it looks really worn out ugly now and the zipper recently kinda broke. It's still my go to at home hobo outfit.

I feel this.

I am also jealous of your Amiga collection. I really miss my Apple //c (flood victim).

My barbell.
Its a cheap, way too stiff thing which I've been using at least 4 times a week for the past 14 years, I should have replaced it many years ago since it has a slight bend it sustained from a 240kg deadlift, its stippling is almost completely gone and its chrome plating is flaking off in the middle (from flexing).
I did all my personal bests and really important milestone lifts on this particular bar, I refuse to get a new one until it snaps or explodes or something. 
The bar and I, we've been through a lot together.  

For me that is what love is all about - taking risks for each other! That helps to deepen the bond! People nowadays are quick to abandon their partner when things get a wee little bit harder or risky or when their partner no longer performs as they used to. That's shallow and sad.

The bar might have a few battle scars, some wear and tear, time may be gnawing on its edges, but its a veteran. I know I can count on it, its familiar quirks give me comfort, the feeling of its rough worn texture reminds me of past victories we shared together and, at the same time, makes me look forward to new adventures we will experience in the future. 
The stippling has been worn away by my hands, leaving my palms grey after each lifting session, yet some of my skin and blood is also embedded in the rough texture of the bar. That bar is part of me, and I'm part of the bar. 

The time may come where I have to retire it, a sad day that will be, but for now its still going strong.

Veeeery nice!

I hope my STAX amp will never break either. It's a midrange model but I think that's fine. I recently auditioned two headphones of the new Lambda line and even though one was about 4 times as expensive as my current one, I like my SR-307 better. It's technically inferior but I prefer the forward midrange. It has a sparkle that no other headphone can match. And I've tried a lot of headphones, some expensive as sin.

I guess I should be happy I found my "perfect" sound. But well, trying out headphones is a hobby of mine. So out of curiosity I'll keep sampling.

But boy, these headphones CANNOT ever break!

I only tried the L300 and the L700. But judging by that I doubt any minor improvement in detail retrieval and soundstage is worth all that money to me. The difference between my $400 model and the L700 that's $1700 new is not big imo. Or my ears are just crap by now. The L700 has the same drivers as their $5000 flagship, so I dunno. I had high expectations for the L700 after all the rave reviews. It HAD to be way better. And to some people it probably is. But I like how my entry level HP sounds. So I decided to save the money and spend it on something worthwhile. Like going new places once the pandemic is over.

I had also taken a photo of my can opener as well but after viewing it I realized I probably have not cleaned it properly for 25 years as well.

I've been meaning to take part in this thread.

Number one is definitely the Swiss Army knife I got for my 10th birthday. It has 15 or so blades and it's always at hand. And it cuts through almost anything; the blades must be pure Adamantium.

Number two would be my mower. I've only had it for four years, but it was made in 1995 and that Briggs engine just keeps on going. The deck is die cast aluminium and I have a fully serviced spare engine for it. That thing will outlive me.

Hmmmm, I don't really have a lot of old stuff I use regularly, I think. Moving between continents has a way of bringing you back down to the essentials.

Oh, I do own quite a bit of old stuff but most of it is stashed at my parent's place back in Europe and I don't use it.

I do use clothes until they start falling apart usually (but that's more of an expression of how much I hate shopping for them). Still have quite a few which I got when I was an undergrad back in the early 2000s.

Like rewindbutton, I used to have really trusty Swiss army knife but I lost it in the stupidest way possible. My parents were visiting me in New York for my dad's birthday and we wanted to go up the Rockefeller Centre the evening of his birthday to celebrate. I forgot that I had the knife in my satchel. When going in, they found it and I only had the choice of not going up (and not celebrating with my dad) or throwing the knife away (they would not let me store it anywhere). So I had to grudgingly throw it into a frigging garbage bin.

Anyway, other than that, I can't think of much. Oh, I have one or two coffee mugs I like and which I had forever but I refuse to get emotionally attached to them because I just know I'll break them eventually (broke my N7 mug just a few weeks ago).