I've occasionally given my horse a wallop then found myself bitterly regretting it as he tanks me round the course in revenge, but usually no. I use them as and when I need to and only when I know I'm capable of using them properly. For example, I never wear spurs because if my horse puts in a big jump or chips in because I've messed the stride up I tend to grip with my heel- if I wore spurs that wouldn't result in a very happy horse.
I can't say I have. Most possibly is when I was doing some work on the ground with Danny, and he booted out sideways at me, at which point he got a slap.... and ran off. Was more just angry because a) I knew I wouldn't be able to hold him and had to catch him and b) he's just not the sort of horse you bother telling off, he just gets offended. Didn't regret it as such, just noted it's pointlessness because of the kind of horse he is.
Occasionally use whips (once/month?) for forwardness when it isn't initially forthcoming. Approx: use legs first gently, then again, then harder, then with whip. Depending what we are doing there would almost always be voice escalation in the mix there too. So, yes, each time it is a failure of our initial communication/partnership, so each time one could say there is 'regret'.
I've NEVER used one on a horse harder than I'd use one on a boy for gentle fun... we're not talking about abuse here.
Saw a top SJ rider give a horse three good belts mid air over a 1.50m oxer wasn't really surprised when horse dropped hind legs and then clattered through the treble afterwards poor bloody animal and that was in public.
Artificial aids are used to enhance the natural aids. A little spur or back up of a leg aid with a schooling whip is infinitely better than nag nag nag with the legs. Too much spur or whip and the horse will let you know about it, tail swishing, head tossing, bucking even. Riders are human and I am sure we all have the whack we regret when its more through our frustration.
As for kids with whips and spurs not a good combination........