Batman Arkham Asylum

To obtain this achievement you must defeat a Titan **without using the Batarang**. I don't know if using other tools will prevent the cheevo from unlocking, but I know that using the explosive gel is fine. Here's what I did:

I missed getting the cheevo during the main story missions so I loaded up the Rumble In The Jungle challenge. After a few rounds of fighting enemies it came down to just Batman versus a Titan. I placed a few explosive gels on the floor as time and the Titan permitted. Then, after the Titan charged, I jumped out of the way and triggered the gel. That caused the Titan to be stunned (the same as if he was hit with a Batarang). Once stunned you pummel the Titan until he throws you off his back. Repeat a few times until the Titan is down. Achievement unlocked.

You can also get this achievement during the fight with Bane. Use explosive gel on the floor and trigger it when he walks over it. Whatever you do don't use the batarang.