In the play "The Merchant Of Venice" by William Shakespeare, the author presents us with a character that most of us usually remember for years afterwards. The question as to why Shylock is so memorable is interesting. Firstly, people may remember Shylock due to Shakespeare's language techniques. The author presents him in vivid images including as a skinflint, as a victim, as an aggressor. Also the language helps us to see him as variously grasping,merciless, vindictive or frail. Another memorable technique by Shakespeare is in the building action - the rising tension, the careful denoument of the good old ever-popular court room drama. One of the last images we have of Shylock is of him sealing his own fate of doom by refusing to show contrition even to save his own life. That is a memorable cliffhanger!
I don't know if this counts as techniques or not, but I think there are two major ways in which Shylock is memorable.
First, I think he's memorable for modern audiences just because he's a Jew. We are so interested in tolerance these days that it is fascinating to see what someone from back then does with a "minority" character.
Second, Shylock is a complicated character. He is not all good or all bad. Instead, he is this interesting mix. On the one hand he is hateful and spiteful. He wants to kill Antonio (or at least risk killing him) and will not take no for an answer. But at the same time he seems quite humane, as in his "do I not bleed" speech. So he is a contradictory character and that makes him interesting.
Shylock a memorable character? We find in the SIGNET edition William Hazlitt's 1818 comment "That he has but one idea[revenge] is not true; he has more ideas than any other person in the piece." Hazlitt also refers to Shylock's "More than a lodged hate" from the court scene which corresponds to Romeo's "O, tell me, friar, tell me, / In what vile part of this anatomy / Doth my name lodge? Tell me, that I may sack / The hateful mansion"(ROM 3.3). The above and other linguistic connections link Shylock and Romeo. Egeus in MND and Capulet in ROM are also angry with their daughters.