[Darth Missingno.]

Walrein has no half-decent options beyond stalling, and Stallrein won't do much against an experienced player, since everyone and their brother knows what it does (and by extension can stop it fairly easily).
As far as spinners go, Starmie, Tentacruel, and Hitmontop are the only ones that really stand out. Forretress is better with Sturdy than with Overcoat even in hail, as long as it has Leftovers, since at full HP it can survive a Fire attack that would otherwise destroy it and spin once (I don't remember if Leftovers recovery precedes Hail damage, or if it's the other way around). I'd be wary of using a Fire-weak Pokemon as a hail team's spinner, though. Which spinner is best depends on the team; I'd recommend an offensive spinner Starmie on an offensive team, bulky Starmie or Tentacruel on balance, and Tentacruel if you're ballsy enough to use a hail-stall team.