Guardians who are into PvP will be delighted with Xur's offerings this week but the items are not particularly useful in PvE modes. Even Gambit got a nice pickup.
Xur is located on Giant's Scar on Io this week. To get to him, go to the aforementioned landing zone, proceed through the giant building and take the path left as you exit. Go that way until you reach a cave on your left side. It contains both Xur and regional chest, so it's easy to find on the map, as you can see on the image below.
The Queenbreaker is the weapon we're getting this week. It's not particularly useful in PvE since the Exotic slot is better used on other weapons while even Legendary power weapons can exceed this one when dealing with mobs and bosses. However, Queenbreaker will one shot Guardians in PvP, no matter how far they are. This is particularly useful in Gambit, where you will be running into the likes of Xenophage and Truth wielders.
Titans are easily getting the best Exotic this week. Dunemarchers excel in PvP as they provide both speed and sliding boost, making it perfect for rushing in for a shoulder charge, shotgun shot or just getting around the map overall. When the passive activates and you then hit an enemy with melee, it will do additional damage to everyone around you. The melee ability doesn't even need to be charged. Get this Exotic, it's your closest thing to Hunters' stompies.
Speaking of Hunters, they drew the short straw this week. Lucky Raspberry improves the Arcbolt Grenade chaining and has a chance to instantly recharge it whenever the bolts chain to another enemy. This sounds great on paper but there are so many better Hunter Exotics for both PvE and PvP.
Getaway Artist can be useful for Warlocks who like some extra damage on the side. It can turn the tide of a duel in PvP so it's useful at times but probably not worth using if you have a better rated Exotic.