Two brands that I've been following on Twitter recently and that have surprised me with their engagement are Muji Indonesia and UGGAustralia. Both not only push out the messages but they also actively engage with people like me, fans and potential ambassadors of their brands.
No surprise that Muji in Indonesia are active on Twitter; Indonesia is one of the largest markets for the social media tool outside of the US. They do the usual corporate thing and announce their sales and product releases but the big difference is when you respond to their tweets they actually respond back. I feel like I am having a conversation with them.
UGGAustralia (ironically not an Australian company, but based in the US), monitor all mentions of their products in the twitter-sphere but also respond and engage with customers, not with the usual single response but at least 2-3 times, developing a real conversation with fans. At least that's how I feel when I engage with them and isn't that the most important thing?