I've added it to various of my fics where it seemed applicable and to individual characters. (I don't know how helpful those'll be, my fandoms tend to be small. I've done Sapphire [S&S], Cally, Jenna, Servalan [B7], Sandra Pullman [New Tricks], Faith Lehane (BtVS), Leela, Jo Grant, Liz Shaw, Peri Brown, Romana, Barbara Wright, Polly, & Charley Pollard [DW], Lynda Day [Press Gang], Miss Marple & Captain Janeway).

Where to use it and not to is a good question, though. I think it probably would apply to more of my fics, but it starts to seem overused at that point, or as if there ought to be levels of awesome...