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No, items are not completely random. I believe they are mostly based on your moves (like if you have 4 special moves it might give you Choice Specs etc.).
EDIT: Just got a Hypno with Belly Drum and no physical moves. I'm pretty sure that's not supposed to happen :/
I got a Gigalith with Sturdy and Focus Sash in a Random Battle. I don't know if this is intentional or not (like Air Balloon Rotom-S and its triple immunity to Ground lololol), but it seems rather superfluous.
My opponent sent out a Sentret with Frisk when my Pokemon had no item (it had used its Air Balloon) and it showed this message:
The foe's Sentret frisked its target and found one !
According to Bulbapedia, if the foe isn't holding an item, no message is supposed to appear.
Some people really need to do their research..
That's the way it works in gen 5. "Simple now doubles the number of stages in a stat change rather than doubling the effectiveness of each boost. ... This also means that using Baton Pass with a Simple Pokémon as the recipient will no longer...
Manaphy used Ice Beam!
It's super-effective! The foe's Giratina lost 75% of its health!
The foe's Giratina was frozen solid!
The foe's Giratina is frozen solid!
[DEBUG] foe-Giratina[L70] move interrupted; movedThisTurn: false.
Rain continues to fall!
Manaphy restored a little HP using its...
Hawntah called Suicune back!
Hawntah sent out Xatu!
The foe's Registeel used Toxic!
The foe's Registeel's Toxic was bounced back by Magic Bounce!
The foe's Registeel was badly poisoned!
The foe's Registeel is hurt by poison!