Best opener?

On my 20+ sin i open with bleed

Depends on what i'm fighting. I'll use knife throw/shadow jump if the mob is in a bunch of aggros, bleed usually then split stream, spark and attack.

Split stream is awesome o.0

I always open with Puncture wound, then i crit the mob like hell, And finish it with Slipstream !

Depends on the situation:

Most often, I like to lead with puncture/slipstream, but I find that the combo is pretty inefficient in practice, because I end up needing to move the extra 2 points of range to get in melee. Slipstream/puncture does the same thing, but sometimes I lose a tick of bleed damage; really not all that big of a deal, but I get in melee without having to pause to walk.

Against casters, either I shadow jump and tackling slash, or I just run up with deep sting to stop cast; both of these put me immediately within melee range, and I follow up with slipstream.

Archers... well, they usually don't hurt once I get within melee range, I usually use my shadow jump/tackling combo, then hopefully slipstream and consequential melee will drop them before root fades. Usually, if root does fade before the mob dies, it's about one hit away and I can knife throw for the kill without having to chase it and eating one or two more arrows.

Rib Strike I use for openings in every pk fight, and sometimes on melee mobs that hit just a bit too hard. I find since that I play without a charm I'm chugging more mana potions than necessary with it (100 mana cost when I first got it was drastically more than anything else I used), but I've since come to understand that mana potions are all of 270 coins each, and that I cover a stack of 100 with whatever set of DQ items I throw at the merchant. I still avoid using Rib Strike whenever necessary however, as it also has the added detriment of turning auto-attack off; which sucks whenever I alt-tab because I'm a set-it-and-forget-it kinda player when it comes to PvE.

Although, with increased life/defense I tend to throw a knife, spark, rib strike/tackling/puncture/slipstream, re-spark, rib-strike, slipstream, and auto-attack. This class is so much fun.

Our skills let us be extremely versatile with our openers and combos...Hard to pick just one. I have few common ways and sometimes special mobs need a little something else...Throw in an extra status (Life, Extra Defense, Ect) and it changes it even further...I love all the options this class has...Really makes you think to be the most efficient you can be on every different mob.
Most common for non runner melee is to Spark, Wind Shield, Puncture, Rib Strike, Tackling Slash to regen the Spark cost...I love Rib Strike but if I can kill them fast enough I avoid it so I don't use up a 6th of my mana just on that XD It's hard to not use Shadow Jump but it can be a waste of chi sometimes with rank 1's range XD

Sparking every mob ftw!

Rib Strike + Spark = dead mob.

Mixed in with Rib Strike + Insert Chi skill here + Spark = dead mob. Sparking on every mob is easy (pre-Adv. Spark, anyway). I stopped using bleed because things died much too easily and quickly even without it. I never use Chill of the Deep in PVE because beating **** to death with a spark is faster. I can see how incredibly useful it'll be in PVP, though.

I don't understand why any Sin wouldn't open with Rib Strike. It saves me from a lot of damage. (The exception being opening with Deep Sting on magic casters.)

I regret every point I put into Slip Stream. There are too many other excellent choices to use in its place that I have little reason to cast it, ever. Maybe Demon/Sage skills will fix that.