With Juggernaut you have three options.
To begin, know that mid game, Juggernaut completely relies on his omnislash to get kills. but later you have a few options.
Option 1: Maximize your Omnislash
If you plan on maxing omnislash, you need two things, attack speed, and an Aghs. The cheapest way to do this is to grab a quick MoM, unfortunately, mask of madness is a unique attack modifier, meaning that desolator will not work while active, and the Mjollnir lightning will make you loose attack speed when it activates. So we go with the alternatives, AC gives great attack speed, and an aura of armor and de-armor that can make or break a right click battle, and does not disable your MoM. Then we have Butterfly, this gives you massive damage during Omnislash as well as Agility and regular attack speed. Aghs gives you an extra three jumps, meaning 33% more Omnislash, and good stats on top of that. Lastly, your Refresher is for those Pudges with 9000 flesh heaps, and so that even the fattest strength carry will melt for you.
Option 2: Become Riki
Your goal here is to catch your enemies jungling their own jungle, or, if you are lucky, your own. The plan is simple, have your pro support ward their jungle, phase boots in after they clear a camp, shadowblade, rightclick once for the bonus damage, then Omnislash and clean up with the necessary right clicks. Shadow blade can also be saved if you are unsure about how well the jungle gank is going to go, and use it to escape if their whole team shows up. (NOTE: dust, sentries, and activating your phase boots will secure your noob-ish death.)
Option 3: **** Omnislash
This is for those ******* teams that 5-man everywhere, instantly crippling your Omnislash. Fight with your team using this build. Use your Abyssal Blade to stun their carry through BKB, use your own BKB over bladefury as bladefury signifantly decreases the damage you can do in teamfights late game, use satanic when your hp is low to scare your enemies into submission,and use daedalus to crit everything.