My second distro was Debian 8, initially with LXDE (which has barely changed at all since then, so it’s still nostalgic) then later switching to KDE Plasma 4. I probably hold the most nostalgia for it, even more than I do for my first distro (Linux Mint 17). For a while I was into Plasma Netbook, which I find to be an especially weird, nostalgic product of its time, and the Oxygen theme in general is probably my favorite default look for any DE.