I didn’t see anyone mention the e-8400, which was near legendary for its overclockability. I remember mine fondly. The Pentium 3 1133 (Coppermine) was also very good for me. First I learned to overclock, and was the first cpu I owned that was over 1Ghz out of the box. I7-4790k. Still have it installed in a secondary system. Too much past its prime to realistically sell. Despite it running on the warm side, with a lot of good experimenting with cooling and voltages and settings, it was a very stable overclocker.
That was the CPU that I chose for my first self built PC. I bought it right on release, literally. First month of 2008, I'll never forget. I was buying the rest of the parts in the month or two before it launched and got the CPU and graphics card last. I spent the early-mid and mid 2000s learning about things while dealing with OEMs that had graphics cards added to them. (Or in some cases, not and using the wonderful Intel "Extreme" Graphics, because omitting AGP slots was popular on some OEMs at the time for some reason!? To this day, my biggest PC disappointment might be seeing the spot where an AGP slot could be, but wasn't, and I was sad with a graphics card I couldn't use.)
At first I thought I'd buy it, put a mild overclock on it, and then just enjoy it for its benefits for a long time. Instead, this thing called overclocking dragged me in more than I expected and I went through a short phase where I was really into it. I "upgraded" to the E8600 that launched later that same year and overclocked it even further. I think somewhere around 4.7 GHz to 4.8 GHz was the wall I met (though it ran farm too warm at those speeds so around 4.3 GHz to 4.5 GHz was probably a more realistic daily speed). I later tried a Pentium 4 641 which was... surprisingly snappy feeling for a Pentium 4, and even suicide feeding that one voltage had me hit the same frequency wall, so I figured I was either cooling or FSB limited. I upgraded the Arctic Cooling Freezer 7 Pro (remember when that was
the go-to in the Core 2 days!?) to one of those "fancy" new heatpipe coolers that would soon become standard, but it mostly brought temperatures down and made things quieter rather than allowing me to overclock more. Which wasn't nothing, because to this day I buy better cooling solely for more quiet and noise-consistent operation and less for temperature or overclocking reasons.
I really planned to run that thing for years and years and years until it was slow before I upgraded again. I wanted to make the most of my first DIY especially. And I would have. However, plans changed.
I won a Core i5 2500K on overclock.net (not trying to advertise, so someone tell me if this is considered doing so and I'll omit the name) in a contest, so that presented an opportunity. I could sell my existing Maximus Formula, E8600, and 4x 2GB 800 MHz DDR2 RAM to fund a new motherboard and RAM for the CPU I had won. I did so, and I ended up with twice the RAM as well (DDR3 was super cheap very late 2011). In a funny twist of fate,
that ended up being the hardware I ran until it was well past its prime, because it lasted from late 2011 until the middle of 2020. I sort of miss the old stuff, but I don't regret making the choice I did to part with it. If anything, I wonder what became of it. It went to a "friend of a friend" of sorts (more like a friend of a member on yet another forum). Years later, I bought another E8600 and still have it in an old Dell. I also tried buying a Q9550 but I was honestly under-impressed with it so I put the E8600 back in.
When I was listing my favorite CPUs, I thought of picking either the E8400 or E8600, but besides being my first and fond for that reason, I don't think I kept them long enough to say so they just narrowly missed getting a mention.
Literally two posts above yours, mate. Though I admittedly didn't call it out by name. I happened to have an E8500.
Ah, the E8500, the often overlooked E8x00 series sibling.
When the lineup launched, everyone ignored the then-top end E8500 and went for the E8400 because it was "the same thing, but cheaper" (the E8200/8300 were also forgotten as they were pretty much only seen in OEMs). Half a year later, the E8600 released and took the place the E8500 had and suddenly I was willing to buy that price point. The lineup ended like that, but there was the rumored E8700, the 3.5 GHz one. Rumors has it that it was canceled since Intel saw no need for a faster dual core (and they were moving to focus on "Core i" instead). I was hoping it would launch, but it's probably good it didn't because upgrading from a E8400 to an E8600 was already silly enough (though it did grant me 4 GHz instead of 3.6 GHz at the same milder FSB settings).