Notes:

HACKER:  They can look like anyone because nobody knows who they are, so feel free to dress in whatever you wish. However, the public's perception of a hacker (per the existing videos, TV shows, etc.) would be someone in a dark hoodie and possibly wearing a mask like Mr. Robot.  Don't worry - after you enter the party and take a few photos - you do not need to keep your mask on - that would be annoying!

COMPUTER SCIENTIST/SOFTWARE ENGINEER/CYBERSECURITY: You could wear a suit  (click here for men's or click here for women's) to look business professional and dress it up with a nerd kit or a pixel bow tie.  Or, wear the floppy disk costume for a laugh!  A third option is to go full nerd!  Any academic-themed character is great with a nerd costume, whether your character's bio says you are a nerd or not :)  Velma is a nerd, so you could wear that and put on a spin. You're at a mystery party, so you are channeling your inner Scooby-doo team to solve the case.

ROBOT/HUMANOID: There are a few options up there with robot costumes, or you can wear all silver and grab a robot mask.  Or even cheaper - wear all black (everyone probably has that in the closet) with the robot mask. Or, even more budget-friendly is to wear all black and make your own robot mask by grabbing your next cardboard box that is shipped to your home. Cut out a window for your face. Paint it silver and decorate it with cut-out felt pieces.  Don't forget the cheesy antenna :)