This is something I've been playtesting in a stall team I've been running on the Suspect ladder, though I'm sure it would work equally well on the standard ladder. I have only tried it with Toxic Spikes, so I'm not entirely sure how well Rapid Spin fits here, or if any secondary attacks should be listed.
http://www.smogon.com/dp/pokemon/tentacruel
[SET]
name: Utility ReSTalker
move 1: Rest
move 2: Sleep Talk
move 3: Surf
move 4: Toxic Spikes
item: Leftovers
ability: Liquid Ooze
nature: Calm
evs: 252 HP / 56 Def / 200 SpD
[SET COMMENTS]
<p>Tentacruel's excellent special defense stat and useful set of resistances (most notably Fire, Fighting and Ice) makes it a good choice to come in on threats such as Infernape, Heatran and Specs Lucario to set up Toxic Spikes. However with no reliable means of recovery Tentacruel can struggle to come in on these attacks repeatedly, and so will not always find the time to set down two layers of Toxic Spikes. The combination of Rest and Sleep Talk allows Tentacruel to replenish any lost health to allow it to come in on these threats again and again, making it much easier to get both layers of Toxic Spikes down. Tentacruel also makes a good switch into a number of the common sleep inducers, most notably Yanmega and Milotic. However, it does struggle against the likes of Gengar (Thunderbolt) and Bronzong (Earthquake) and can do very little back to Roserade, who sponges Surf easily and can also remove your Toxic Spikes upon switching in. </p>
<p>If you don't feel that Toxic Spikes are necessary for your team, then there are several other options for the last slot, most notably Rapid Spin. With this set, Tentacruel makes an excellent spinner, being able to come in repeatedly and clear entry hazards. However, apart from Gengar, Tentacruel struggles to do anything to most anti-spinners, and when you consider that Tentacruel already clears Toxic Spikes upon switching in, it becomes a much less attractive option. Despite this, it is still worth considering if your team dislikes Stealth Rock or Spikes. Sludge Bomb gets STAB and excellent coverage with Tentacruel's Surf, and hits Abomasnow and Celebi hard. Ice Beam hits Salamence, Garchomp and maintains some coverage on Celebi, whilst Hidden Power Electric actually does something to other Water types, most notably Starmie and Gyarados. However, a utility move is recommended as otherwise Tentacruel's role in a team can be somewhat limited. It also helps to differentiate Tentacruel from other bulky waters who can run a similar set, most notably Milotic and to a lesser extent Gyarados.</p>
http://www.smogon.com/dp/pokemon/tentacruel

[SET]
name: Utility ReSTalker
move 1: Rest
move 2: Sleep Talk
move 3: Surf
move 4: Toxic Spikes
item: Leftovers
ability: Liquid Ooze
nature: Calm
evs: 252 HP / 56 Def / 200 SpD
[SET COMMENTS]
<p>Tentacruel's excellent special defense stat and useful set of resistances (most notably Fire, Fighting and Ice) makes it a good choice to come in on threats such as Infernape, Heatran and Specs Lucario to set up Toxic Spikes. However with no reliable means of recovery Tentacruel can struggle to come in on these attacks repeatedly, and so will not always find the time to set down two layers of Toxic Spikes. The combination of Rest and Sleep Talk allows Tentacruel to replenish any lost health to allow it to come in on these threats again and again, making it much easier to get both layers of Toxic Spikes down. Tentacruel also makes a good switch into a number of the common sleep inducers, most notably Yanmega and Milotic. However, it does struggle against the likes of Gengar (Thunderbolt) and Bronzong (Earthquake) and can do very little back to Roserade, who sponges Surf easily and can also remove your Toxic Spikes upon switching in. </p>
<p>If you don't feel that Toxic Spikes are necessary for your team, then there are several other options for the last slot, most notably Rapid Spin. With this set, Tentacruel makes an excellent spinner, being able to come in repeatedly and clear entry hazards. However, apart from Gengar, Tentacruel struggles to do anything to most anti-spinners, and when you consider that Tentacruel already clears Toxic Spikes upon switching in, it becomes a much less attractive option. Despite this, it is still worth considering if your team dislikes Stealth Rock or Spikes. Sludge Bomb gets STAB and excellent coverage with Tentacruel's Surf, and hits Abomasnow and Celebi hard. Ice Beam hits Salamence, Garchomp and maintains some coverage on Celebi, whilst Hidden Power Electric actually does something to other Water types, most notably Starmie and Gyarados. However, a utility move is recommended as otherwise Tentacruel's role in a team can be somewhat limited. It also helps to differentiate Tentacruel from other bulky waters who can run a similar set, most notably Milotic and to a lesser extent Gyarados.</p>