Something kool:
A weird boat model can be found by noclipping under the HL2 map d3_c17_02
Once you crowbar the boat G-Man pops up with a crow on his shoulder very weird indeed
Have a look for yourself...
Spooky... Maybe it is under other HL2 maps...
Also another weird thing...
In map d3_c17_05 there is a cube high above the actual playable area...
In this box there is Breen and hes reciting words I could not hear because, well, frankly my speakers weren't plugged in