Todays evil robot is...

Ash

Ash (played by Ian Holm) was the science officer aboard the Nostromo in Ridley Scott's Alien and was indirectly responsible for the deaths of all the crew except for warrant officer Ellen Ripley. Ash begins the film as a quiet and mild-mannered man though Ripley has her suspicions about his true intentions. Suspicions that turn out to be well founded when it's revealed, in a very graphic and shocking way, that Ash is in fact an android and that he sweats milk.

Up until this point things had been pretty plain-sailing for this happy-go-lucky space misfits bunch. Believing that 'Mother' (the ships computer) had awoken them from their hypersleep to carry out a routine check of an unidentified signal apparently eminating from a vessel on the surface of a nearby planet, they toddle off all smiley and curious to check it out. Then - BAM - it all goes tits up. John Hurt gets a squiggley, clawy moster on his face that lays and egg in him. John bursts whilst at dinner and a penis with teeth pops out of him and scuttles off. Sweet. The titular alien grows bigger and nastier deep in the bowels of the ship until he gets hungry and starts wolfing down the crew in some of the most tense and scariest scenes ever commited to film. I used to have nightmares about being stuck in an airshaft with the damned thing like Dallas.

Whilst all of this is going on Ripley discovers that Weyland-Yutani Corporation (yet another nefarious, evil mega-company that always crop up in this type of film) knew about the possible danger and instructed Ash to bring the creature back to Earth no matter the cost. Special Order 937 instructed Ash that all the crew were expendable, from that point on everything he did he did to protect the alien organism. Now the crew have an alien, a missing cat and a dodgy robot to deal with. It never rains eh...

One of the finest scenes in the film comes when Ripley discovers what Ash is up to and Ash tries to do away with her by giving her a good slapping and then, in a very Freudian gesture, tries to kill her by forcing a rolled up magazine down her throat. Luckily Lambert & Parker (two other members of the crew, not a passing accountancy firm) are on hand to help and Parker knocks Ash's block off revealing that his innards are in fact full of mayonnaise, spaghetti and fishing floats. Human he 'aint.
Ash rolling around the room vomiting white fluid whilst 'spazzing-out' and attacking Ripley, Parker & Lambert is one hell of a gruesome scene and when they switch him back on to question him about the alien's possible weakness, his evilness and lack of consideration for the crew become apparent when he calmly says "I can't lie to you about your chances, but (smirking) you have my sympathies." Brilliant.