Either Crytek are quietly trying to cause no end of hell for EA, or the wrong Crysis demo got released and there are a whole lot of panicking, screaming, crying German developers right now.
First, the script for the entire game was discovered lurking in the demo files. Then a simple config file edit activated supposedly DirectX 10 and Vista-only graphical effects in DirectX 9 and XP. And now, someone faffing about with the bundled level editor has managed to dump a load of good stuff from later in the game into the demo map and make it playable. To find out how, what, who and wither, you'll have to read on...
What's in there? Guns. Lots of guns - the game's entire repertoire (as well as an impressive selection of various explosives), it appears. Tanks, boats, assorted military vehicles and ridiculously powerful helicopters (which handle a little like Battlefield's, and are hilarious overkill against the still popgun-armed Korean dudes). And one of the much-mooted aliens. If you want an early taste of what these flying tentacle laser-horrors are like to fight, and how the game's human NPCs react to them, this'll do it. Oops.
You want 'demofunmap #5' from here, the work of canny German modder siLe`. Extract the level.pak file and dump it into C:\Program Files\Electronic Arts\Crytek\Crysis SP Demo\Game\Levels\island. Either overwrite the exisiting level.pak in there, or rename it to something with a different extension (e.g. .old) if you don't wanna have to reinstall the demo later.
Then, start a new game in the demo (yes, you'll have to do the cutscene'n'parachtute drop hoopla again) - be warned that apparently it only works on the Normal difficultly setting - and keep playing until the bit where you find your mate all Predatored up in the trees. Start following the objective arrow, and you'll soon find a table full of a goodies, and an angry alien in the skies. Just beyond the table is an enemy encampment, and a short run to the left of that is vehicle and many-gun heaven. Clearly, this may spoil some of the full game for you. But in the relatively open environment of the demo's island map, it allows for mega-playtime. Be warned that approaching the centre of the map in a chopper triggers the final cutscene and ends the demo, though.
Thanks to Gestalt for pointing this out, and apologies for not noticing sooner.