Mounts and run by

I know as posted, amulet of nec clickie stops a horse dead if you click the illusion.. Guessing other insta click illusions would do the same.

hobby horse has zero momentum slide

As others have mentioned /dismount does it as well. But non-illusion insta-clicks will not stop you on a dime. The reason why AoN & /dismount stops you is because the model changes.

No, he died, but he did go flying off his mount was the point...

Tried it out.
Both snail and carpet from TBL appear to stop instantly. I.e. if I start casting immediately upon releasing forward, there is no interrupt.

The rhinos from EoK (the gray one in premium and the gold one for group content progression) have quite a bit of momentum.

Interestingly enough, my SK's lvl 85 AA horse also seems to stop on a dime.

The TBL carpet you get from doing all the quests definitely does not stop instantly while in combat. It's what I use on my warrior and I never use it in combat for that reason.

I wish the amount stop by pass point were even more than it is now.

I agree...I hate this garbage. If I am in a full run and want to stop and cast it takes a good 3-4 seconds easy. As far as I can tell my mount isn't a '77 Cadillac, so get rid of this bs.