You can use any weapon you summon with your Pact of the Blade feature as a Spellcasting focus for your Warlock Spells.
In addition, the weapon gains a +2 bonus to its Attack and Damage Rolls, unless it is a Magic Weapon that already has a bonus to those rolls.
Finally, the weapon you conjure can be a Shortbow, Longbow, Light Crossbow, or Heavy Crossbow.