Smly:
Is there another way to press keys without using the keyboard.h? I saw some random things on the internet using "buf" or something, is that possible?
When you code a USB-chip Arduino as HID, you can easily send keyboard, mouse, and/or stick data to the PC as part of your sketch. Just what the sketch takes as input is up to you, buttons or sensors don't matter, timing if you want, and when it's time to send to PC, it looks like a generic game controller to the PC.
PS -- if you want a keyboard & mouse connected, the Arduino Playground has how-to to connect PS2 mouse or PS2 keyboard right to Arduino pins. Walmart sells Logitech PS2 keyboard&mouse for $12.