If you closely observe your Player Frame, u will notice that your Energy (also your HP) ticks every 2 seconds. This tick will keep on ticking no matter what you do and even when your hp or energy is full. By carefully executing a move milliseconds before your Energy bar ticks, you could get "20 extra Energy". Therefore you could:
Backstab twice after Cheapshot (Without Vigor or +10 energy set bonus):
You need the talent "Dirty Deeds" to have you Cheapshot REDUCED TO 40 energy. Time your Cheapshot then Backstab your target, and just before the 4 second Cheapshot stun wears off, you should have enough time to land another Backstab. Works best against NPCs (e.g. mobs)!
If this is done correctly, after your Cheapshot, you should immediately see that you have 80 energy points (80%) instead of 60(%). Then as you backstab, another energy tick should happen which will give you 40(%) energy, and then another tick which gives you 60%.
Another variation, A unreliable stunlock: If you have the Sealfate and Relentless Strikes talent, when your Cheapshot and Backstab (crit) achieves you 5 combo points, you could choose to Kidney Shot then land 2 backstabs. A 4 or 5 point cold blood eviscerate could follow.
Land a Backstab immediately after an Ambush
This could be done even without the 120 max energy (from Vigor (+10 energy talent) and the +10 energy set bonus from Nightslayer or the Arena 2 set). Its a little hard to time yet you could kill clothies before they could even react. This is even deadlier with the 120 energy i mentioned since you could land a 5 point Coldblood + Eviscerate a few seconds after.
Silencing Garrote + Backstab + 4/5 point Coldblood + Eviscerate
A little of a stretch but...a classic injured mage killer. Achieve 5 point Eviscerate with "Premeditation". Mages wont be able to Blink away when they are silenced, but they could still use Ice Block.
There are more possibilities of this trick(s) it is even better with the said "110 or 120 max energy"...! Druids please refer to your cat-form equivalent skills.
There are also interface addons that will display your energy ticks such as: Gonffbar (Ace2) and Energy Watcher.
Even without these addons, you could look at your HP-tick as a reference.
Proof: http://youtube.com/watch?v=2cy76T11sXw
10 mb Higher Quality: http://rapidshare.com/files/47223108/Untitled.avi.html