Useful list. One thing worth adding for anyone copying the party member line: $gameParty.members()[1].isAlive() throws a TypeError when the party has only one member, and a script error inside a conditional branch stops the game. A guard keeps it safe:
$gameParty.members()[1] && $gameParty.members()[1].isAlive()
Same idea for $gameMap.event(5). It returns undefined on any map without an event 5, so a common event that runs on several maps can crash on it.
A few we use a lot, all fine in MV and MZ:
Another event's self switch (event 5, switch A, this map):
$gameSelfSwitches.value([$gameMap.mapId(), 5, 'A'])
Anyone in the party knows skill 10:
$gameParty.members().some(a => a.hasSkill(10))
Actor 1 has state 4:
$gameActors.actor(1).isStateAffected(4)
Player is in any vehicle:
$gamePlayer.isInVehicle()