"Dragon Effect", from detractors. Some people don't mind the connotations at all.
The female Hawke is called Lady Hawke by some of the fanbase. "Mike" is a favorite name for Male Hawke, for some reason...
Also, a Hawke with a diplomatic/nice personality is sometimes called "Paragon!Hawke", while a Hawke with an aggressive/serious personality is called "Renegade!Hawke." A Hawke that usually takes the middle dialogue options and develops a sarcastic personality is often called Silly!Hawke.
New companion Tallis has recieved the nickname Kasumi due to the similarity of their DLCs.
As an additional note, the Japanese version of Dragon Age II is the first game of the Dragon Age saga with Japanese voice acting, since the prequel only had the original English voices with Japanese subtitles and text translations for everything else.*
In fact this is the first BioWare game with any Japanese voice acting at all, since their other games weren't released there or without Japanese voice acting. It had something to do with the fact this game will be released in Japan by Spike and not by EA's Japanese branch unlike their other games.
Isabela has a different voice actress, since her voice was exactly like the character her previous voice actress played, Queen Anora.
Merrill has a different voice actor in the second game since the Dalish now have Welsh and Irish accents.
Anders too. Previously voiced by Greg Ellis, who also voiced Cullen (in both games), he is now voiced by Adam Howden (heard as Silas Corthwaite in Leliana's Song) because unspecified "shenanigans" made it impossible to hire Ellis for such a large role.
The boss fight against Orsino was originally going to be exclusive to the Templar endgame. However, it was added to the mage endgame for the sake of another boss fight.
Anders' cat Ser-Pounce-A-Lot was going to still be around, walking around in Anders' clinic. However, he was cut since it would require making a new character model.
The Exiled Prince DLC was originally going to have Nathaniel Howe play a major role. While Nathaniel can still appear in the main game, he was cut from the DLC due to the possibility of his death in Awakening.
Much like how Origins has Awakening, Dragon Age II was going to have an expansion pack called Exalted March but was canceled due to other projects.