has he ever used Mjolnir to build anything?

He built a tower of woop ass after Civil War when he found out Stark cloned him. Does that count?

HA HA,

You know I have never even once considered that. I'm looking forwards to seeing the responses.

He built a tower of woop- damn it somebody stole it already. Ahhhh got it, Thor once built a hole in the sky to summon a giant ass thunderbolt. Does that count?

He built this city on rock and role

He actually forged some chains at one point in an old JIM story. they are used to bind loki.

that's it so far?

thor really needs to start using Mjolnir to forge things.

@sunhawk: He also forged some arrows to Hawkeye once.

I remember him using it as hammers are typically used during an Avengers/Inhumans team-up in "Avengers Annual" #12 (1983).

I don't recall what they were building (a ship, perhaps?) but it was made of wood.

if he wants to forge something, he calls on the carpenter jesus.