To be honest, I'm not sure I see the point in Fake Out at all on Sneasel. The most commonly-used leads that use a Sash are Electrode, Froslass, Dugtrio, Cloyster, and Alakazam.
Electrode: You will never be able to stop it from using RD and then Exploding on you, even if it Taunts first.
252 Jolly Fake Out vs 0/0 Hasty Electrode: 20.3% - 24.1%
252 Jolly Pursuit vs 0/0 Hasty Electrode: 30.3% - 36%
24.1 + 36 + 36 = 96.1%
Dugtrio: Leads usually carry Protect to stop Ambipom's Fake Out, so you'll never be able to break their Sash unless they have no idea what moves Sneasel learns.
Froslass: Immune to Fake Out.
Alakazam: If it carries Inner Focus, it will be immune to flinching anyways. If it has Synchronize, I assume it would have Protect in order to stop Ambipom's Fake Out anyways.
Cloyster: Because of the shoddy glitch that enables Rock Blast to kill through Focus Sash, Fake Out is useful so you can take its Sash out AND Taunt it, but once that glitch is (presumably) fixed in Shoddy 2, or if you're playing on WiFi, it won't be needed since even if they Rock Blast as you Taunt, you will live due to Focus Sash and can proceed to attack it.
I think Night Slash or Ice Shard would make a better candidate for the slot. Ice Shard would be useful for taking out slightly weakened RP Torterra, Swellow, or Dugtrio, while Night Slash is simply harder-hitting STAB than Pursuit if the enemy doesn't switch out, or, in the case of Uxie, you are facing a slower U-Turner.
Electrode: You will never be able to stop it from using RD and then Exploding on you, even if it Taunts first.
252 Jolly Fake Out vs 0/0 Hasty Electrode: 20.3% - 24.1%
252 Jolly Pursuit vs 0/0 Hasty Electrode: 30.3% - 36%
24.1 + 36 + 36 = 96.1%
Dugtrio: Leads usually carry Protect to stop Ambipom's Fake Out, so you'll never be able to break their Sash unless they have no idea what moves Sneasel learns.
Froslass: Immune to Fake Out.
Alakazam: If it carries Inner Focus, it will be immune to flinching anyways. If it has Synchronize, I assume it would have Protect in order to stop Ambipom's Fake Out anyways.
Cloyster: Because of the shoddy glitch that enables Rock Blast to kill through Focus Sash, Fake Out is useful so you can take its Sash out AND Taunt it, but once that glitch is (presumably) fixed in Shoddy 2, or if you're playing on WiFi, it won't be needed since even if they Rock Blast as you Taunt, you will live due to Focus Sash and can proceed to attack it.
I think Night Slash or Ice Shard would make a better candidate for the slot. Ice Shard would be useful for taking out slightly weakened RP Torterra, Swellow, or Dugtrio, while Night Slash is simply harder-hitting STAB than Pursuit if the enemy doesn't switch out, or, in the case of Uxie, you are facing a slower U-Turner.