My ZZ is indestructible. I've had it for about 5 years. It's in a dim corner and gets watered a few times a year, if that, and has never been fertilized.

So far? Probably a tie between Yucca guatemalensis (spineless yucca) and Euphorbia tirucalli (pencil cactus). I've had one of the former (which has turned into five) since 1998ish, and one of the latter (which is still only one) since 2001. They've both been neglected, rootbound, without any sun, in bad soil, overwatered, surrounded by raging insect infestations, etc., and neither one has ever done anything worse than dropping a few leaves (Yucca) or stems (Euphorbia).

Neither plant is good for everybody: Euphorbia tirucalli is somewhat dangerous, and Yucca guatemalensis is often sold as somewhat fragile, barely-rooted canes which aren't well-established in the soil and are easily overwatered as a result. But if you get a good, solid, well-rooted plant to begin with, and treat it remotely well, it'll be fine.

Mother-in-law tongue, or Sans!

That thing gets treated just like how karyn1 described..

As long as I forget to water it, it lives!

Mike

Aloe, and a couple of dracaenas that someone left at my house. The aloe got completely neglected because it actually tried to kill itself: it took a tumble off the side of my desk and beheaded itself. I kid, but it kept growing in a spiral off to the side until it was just too lopsided, hence the fall off my desk. I just stuck it back in the pot, since it had a few roots left and I didn't know what else to do with it. Then I moved, and had no place to put it for a while, so it sat around vaguely near a north window for months, and still survived that. It is still here, about 3-4yrs later, but now it is repotted and in a south window. It has produced numerous pups. One of the separated pups is looking like it is trying to do the same thing: grow off to the side. Sigh. I've got all escape routes blocked off at the moment.

The dracaenas were picked up on the side of the street on trash day by someone who helped me move. He said he'd come back for them but never did. These had barely any soil, got blasted by the sun for a summer, never watered, moved into a basement with almost no sun and no water for an entire winter and tossed back outside in the summer. After a couple years I decided it was so tough, it deserved better so I repotted one set, lopped off the tops of the other set and restarted them, and they are also still here today.

I have killed numerous spider plants. I don't know what it is. I think it is this house. I never had problems with them before until I moved here.

It's a tough call between my Aloe ciliaris and my Saxifraga sarmentosa.

Aloe is sitting in a 6" plastic pot with virtually no soil, I haven't watered it in ages, it's leaning very badly and it clustered behind a bunch of other plants under the grow lights. I really like the plant though so when it warms up I'm going to repot it, cut it in half and give it some support so it grows straight...oh and a wee bit of water.

The Saxifraga isn't nearly as badly neglected but I forget to water it WAY more often that it probably likes, and yet it grew like a weed and put out a gazillion runners! Then when I was moving it over to my new house a few days ago, the bottom of the box it was in popped open spitting it unceremoniously onto the ground....smooshed the poor thing...but it's still kickin'!

The Aloe coincidentally enough was in the box too. Both are about a year and a half old.

I might have said my euphorbia tirucalli but I finally did manage to kill it. Now I feel bad. That plant grew from a little 5" cutting into a 6' monster. It had been left in the basement for a year with no care what so ever and still looked good. That plant could live and even thrive thru almost anything except freezing temps and 5 feet of snow. Yep, I forgot to bring it in last winter.

Hey, it's all right. I lost the ability to overwinter Sansevieria trifasciata a few years back, and they've been dropping like flies ever since.

(No, I do not know how one loses the ability to overwinter a houseplant. It just happened.)

The oldest one I have in my collection is a cycad (Cycas revoluta)--must have had it for over 25 years.