There are so many I like but I only occasionally make any particular one, except a mesophilic yogurt that I keep a quart of going at all times. Most of my ferments a batch lasts a long time so I don't practice making any individual one very often.
Salted lemons - I thought they were too old to use, most recipes call for using them within a couple of months, but then I found the Asian recipes that say they're better after a decade.
Sauerkraut, usually with experimental seasonings (citrus peel, ginger, galangal, fennel, weeds from the garden,...). Been a long time, there are too may good ones at the store now, and mine gets really soft and sour before I finish a batch.
Kombucha, both black tea, and (my favorite)
root tea: sassafrass, sarsaparilla, burdock, star anise. Have to get a new scoby, it's been too long. I can't drink it fast
enough to keep up when I make it often enough to keep the scoby happy.
Plum wine from my formerly superabundant plums.
Dilly beans. Yay! One of the few vegetables I harvest enough of to preserve. Brine.
Mushrooms. Last year I got a bunch of lactarius near my house. Brined some. Packed some in miso. Yum. Particularly recommended for fans of pickled herring.
Umeboshi have not yet been really successful.
Olives. Some just in brine, some in brine after lye.
Sourdough bread. I fade into and out of wanting to make my own bread, so I often have to start a new starter.
Oolong tea from home oxidized tea leaves. Unsure whether they're fermented or just bruised. Similar with fireweed. I try to keep them moist enough to ferment a little.
Sour cream from my yogurt starter when I have leftover cream.
I tried artichoke hearts in brine this year but last time I tasted them they were too tough, several months ago.
Alexanders stems in brine.
When I buy nukazuke or kasuzuke I put more vegetables into the leftover nuka or kasu. Too lazy to make a nuka pot.
Kvass. Love it. Beet or bread, either or both. Too much hassle but I miss it.