Rigidbody.useGravity

Description

Controls whether gravity affects this rigidbody.

If set to false the rigidbody will behave as in outer space.

var coll: Collider;

function Start() {
	coll = GetComponent.<Collider>();
	coll.isTrigger = true;
}

// Disables gravity on all rigidbodies entering this collider.
function OnTriggerEnter(other: Collider) {
	if (other.attachedRigidbody) {
		other.attachedRigidbody.useGravity = false;
	}
}

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    public Collider coll;
    void Start() {
        coll = GetComponent<Collider>();
        coll.isTrigger = true;
    }
    void OnTriggerEnter(Collider other) {
        if (other.attachedRigidbody)
            other.attachedRigidbody.useGravity = false;
        
    }
}