Interesting, looks a little bit like pachira.

I did the same thing as you with avocados and mangos. I also tried sapote, but they kept getting mold on the seed casings and I gave them up for goners. A few months later I looked at the plastic bag they were in and discovered their now-dead roots that had formed after I started ignoring them completely (I kept forgetting to check the moisture level before that, thought that was another nail in their coffin, but was wrong!).

I'm resisting the urge to try and grow cherimoya the same way...they look like they grow way too fast! Ditto for jackfruit.

Oh, my most successful random seeds so far are tamarinds, but those sometimes come up as bonsai, and lots of folks grow them from seeds.

My lemons from seed also look pretty nice, but those are common in containers (though usually the actual good fruiting varieties rather than the who-knows-what-probably-inedible lemons that I'm growing!)

Right now I'm working on some guavas (and passion fruit) from seeds that my girlfriend's mother brought back from Hawai'i.

That reminds me of some of my failures..I tried growing a beach plant from Maui (Carissa macrocarpa), and despite only having one seed that germinated, I almost made it, but I think I killed it with ignorance by putting it in pure perlite and probably paying too much attention. Whoops!

Oops, Carissa macrocarpa is natal plum...I meant Scaevola taccada (beach naupaka).

Oh, another weird one that was inspired by a trip Hawaii--I'm trying to grow sea grape (Coccoloba uvifera).