In my opinion, Zebstrika's best niche is Sap Sipper + Overheat because no one else can run this. It's a perfect check against Serperior, Ferrothorn and Breloom, and even Whimsicott, being able to switch into their Nasty Storms, Power Whips, (Stun) Spores and others. I've been running this set with acceptable success:
Item: Life orb / Expert belt
Ability: Sap Sipper
Nature: Naive (+Spe, -SpD)
EVs: 72 Att / 188 SpA / 248 Spe
- Wild Charge
- Overheat
- Hidden Power Ice
- Double Kick
Odd distribution of EVs, but are given mainly to ensure a OHKO on a 252/252+ Ferrothorn with Life Orb and Overheat and to outspeed max speed Starmie. Remaining EVs in attack. With Expert Belt you have to invest more on SpA reducing your attack EVs. HP Ice is for incoming Garchomps, Salamences, Gliscors who expect an Overheat/Electric move. I'm running this set at the moment, but I'm never sure about the last move... With one Sap Sipper boost, Double Kick OHKOs Tyranitar and its also a 2HKO against incoming Hydreigons and Heatrans that expect Overheat. I've tried Me First, but I think it's a bit situational. Thunder Wave is another option but you're walled by the same ground-type foes that switch in expecting a Wild Charge. Pursuit is not a bad option, but without STAB and no max attack there are other better users for that move.
Zebs takes hits like a wet, rotten piece of paper, but thanks to that speed, unpredictability, coverage, and the possible attack boost thanks to Sap Sipper I've been able to get tons of WTF moments.