Third-ing Artimud. I also really like the Field Paste made by the same folks (Red Horse Products). I find it sticks a little better for horses that are turned out in areas that are sloppy. It has more honey in it so is stickier. It got us through some really gnarly wet winters the last couple years, where there was still gross poo-mud in some areas they chose to stand despite having $10k worth of hardstanding available to them. I would consistently find evidence of it still in collateral grooves a week after application in really sloppy conditions.
I use Artimud primarily under shoes and boots, and would use it over Field Paste in horses that are going to be stalled for a few hours at a time or who will be in fairly dry conditions.