3' on my 14.3hh 23-yr old gaited Paso Fino gelding. Yep, THE best horse. My eventing prospect has great scope over the very low fences but I haven't tried him over anything higher than 21". He's a leggy 16.2hh TB and will probably be able to jump around 4' when he fills out :) SO excited for that!
I've jumped 2'9" in lessons on my 16.3 Appendix...he doesn't even really have to try, cause he's so tall. Anything under 2'6" he won't really jump, he just steps over it 'cause it's not challenging enough.
I've gone 2'9" with my gelding, he can go 3'3" but I've never taken him that high, I left the eventing barn before I could get that high and the last barn I was at, I didn't take lessons that much. I'd like to see how he does at 3", at 2'3" he doesn't even make an effort, he just canters over them.