Drop a trigger from an Oracle database using Liquibase (http://www.liquibase.org).

drop_trigger_changelog.xml

<databaseChangeLog
  xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:ext="http://www.liquibase.org/xml/ns/dbchangelog-ext"
	xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog ../../xsd/dbchangelog-2.0.xsd
	http://www.liquibase.org/xml/ns/dbchangelog-ext ../../xsd/dbchangelog-ext.xsd"
	logicalFilePath="drop_trigger_changelog.xml">

	<changeSet id="1" author="stefanborghys" runOnChange="true">
		<preConditions onFail="MARK_RAN">
			<sqlCheck expectedResult="1">
			SELECT DECODE(COUNT(*),0,0,1) FROM DBA_OBJECTS WHERE OBJECT_TYPE = 'TRIGGER' AND OBJECT_NAME = 'TRIGGER_NAME';
			</sqlCheck>
		</preConditions>
		<comment>Drop a trigger from an Oracle database.</comment>
		<sql><![CDATA[DROP TRIGGER TRIGGER_NAME;]]></sql>
		<rollback>
			<![CDATA[
			create or replace 
			trigger SCHEMA_NAME.TRIGGER_NAME
			BEFORE INSERT OR UPDATE ON TABLE_NAME
			BEGIN
			-- The trigger's logic
			END;
			]]>
		</rollback>
	</changeSet>
</databaseChangeLog>

You can use the same syntax should you wish to drop an Oracle package. There aren't many in the wild but still good to know. (e.g.