Here's some basic code you could use as an example (I haven't tested it, so bear with me here).
;; Basic Setup C = CreateCamera() S = CreateSprite() T = CreateTexture(16,16) ;; Create cross-hair texture SetBuffer(TextureBuffer(T)) Color 0,0,0 Rect 0,0,16,16,True Color 255,255,255 Rect 0,0,16,16,False Line 8,0,8,16 Line 0,8,16,8 SetBuffer(BackBuffer()) ;; Set up cross-hair sprite EntityTexture S,T,0,0 EntityOrder S,-100 EntityBlend S,3 EntityParent S,C,0 PositionEntity S,0,0,100