wrote:
I just moved into this new high rise apartment and I'd like to hang
some stuff up. Mostly a few small paintings, but also a few heavier
(6.5 pounds/3kg) masks off the walls.

I suggest either of these:

http://www.leevalley.com/hardware/pa...914,50630&ap=1
http://www.leevalley.com/hardware/pa...914,50630&ap=1

The first comes in a range of sizes and uses finishing nails to support
up to 75lb, the second is a single item that supports up to 50lb.

As others have said...small puncture marks are easily hidden, but
adhesive-based methods are hard to fix.

Chris