What is the most successful direct marketing (mailers)group you've had success with?

[Aria Khosravi]

I thought I would start a conversation on what area you have had the most success with in regards to direct marketing mailer. I have had minimal success with NOD's but I suspect everyone targets these people. I am about to kick off a new mailer campaign, but i'm not sure which group(s) to target. What group do you get the best response from?