Kobe Bryant actually started out signing full autographs pre-NBA and also his rookie year (see non-NBA licensed products Press Pass and Score Board), then switched to "Kobe 8" and "Kobe" throughout many years (Topps, early and mid-UD products). After that, he switched back to signing full autographs for most late-UD products, along with occasional "Kobe". After joining Panini in 2009, Kobe mostly signs full autographs for private, closed-door signing sessions (i.e. signing for trading card products/memorabilia brand/paid send-in's).
For in-person ones, Kobe also started out signing full autographs early in his career (at times even adding jersey number), then switched to "Kobe 8" / "Kobe" / "Kobe 24" . In situations where a lot of fans are in the public trying to acquire his autograph, he even simply signs "KB" .
Personally, I like the "Kobe 8" and full autograph the most, but as many of you can see, even for full autographs, Kobe seems to start signing sloppily now - not quite surprised given how many cards/items he has signed for Panini.