I'm sure everybody who reads this thread is probably going to say lifter tick, which is normal and since your car is stock (no mods listed in your profile) it's probably not the downpipe making the noise. I had a tapping with my car that got progressively worse and it turned out to be a cracked flange on my aftermarket uppipe.
chances are there's nothing wrong with your lifters. the ticking sound is a characteristic of these boxer engines, especially when they first start up.
ditto mines been ticking from day one and i bought it brand new.. its got a little louder since then ... but there in actruallity nothing wrong the boxers are are just loud i actaully kind of like it... it gives it characteristic