Stevan Seagal of course is a name synonymous with aikido and responsible for bringing many a student to the door of the door. Whilst his acting skills are sometimes called into question his martial prowess is beyond question. Other actors into aikido include Anthony Lapalia but as an 'Serious Actor' rarely does he do action films. Wesley snipes is another actor who does jujitsu (well movie do) but it looks like aikido at times so we can all enjoy.
Well before any of the modern films though the young guns of the early aikido made their own foray into film.
Aikido is fortunate that although based on an ancient art it is a relatively modern incarnation and so there are many videos of the aikido and the early masters practicing aikido. The aikido Journal has gathered many of these and you can see them on youtube sometimes