The Collaborative International Dictionary of English v.0.48:

emotionless \e*mo"tion*less\ adj.
   1. unsusceptible to, destitute of, or showing no emotion;
      unmoved by feeling. Opposite of emotional; as, he kept
      his emotionless objectivity and faith in the cause he
      served. [Narrower terms: matter-of-fact, prosaic;
      philosophical, philosophic; phlegmatic, phlegmatical,
      stolid; stoic, stoical; unblinking] Also See: cool,
      passionless, unmoved(predicate), unmoving.

   Syn: unemotional, passionless.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

unblinking
    adj 1: showing no visible emotion; "stood unblinking and
           accepted a sentence of a year"
    2: not shrinking from danger [syn: unblinking, unflinching,
       unintimidated, unshrinking]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "unblinking":
   agile, alert, alive, attentive, awake, bright, calm, coolheaded,
   inexcitable, keen, nerveless, nimble, on the, on the alert,
   on the ball, on the job, prompt, qui vive, quick, ready, relaxed,
   rock-steady, sharp, sleepless, smart, steady, steady-handed,
   steady-nerved, steel-nerved, strong-nerved, unabashed, unappalled,
   unawed, unblenching, uncowed, uncringing, undaunted, undismayed,
   unfaltering, unflinching, unintimidated, unnervous, unnodding,
   unquivering, unshaken, unshaky, unshrinking, unsleeping,
   unstrained, untremulous, unwavering, unwinking, wakeful,
   wide-awake, without a tremor