You should probably clarify whether you mean objectification in media (i.e. one dimensional portrayals of individuals as sex objects and personality voids, existing only to be admired aesthetically and/or desired sexually...seen most frequently in porn, but also in mainstream media and advertising) or objectification in person, which means treating someone like an object to be used for your sexual stimulation or gratification without any regard to their worth or value as a human being. This can manifest as anything from "using" someone purely for sex, to date/stranger rape, to the molestation of infants.
As to how it feels...I would imagine it feels very much like everything about you has been stripped away, and the only thing of value is whether or not someone finds your appearance sexually exciting. I suppose it's possible that for some people in the throes of serious sexual addiction this might feel rewarding (whilst contributing to their pathology), but for most it would be an extremely dehumanizing experience.
In the case of the media portrayal...which given this is primarily a video game forum is almost certainly what you are referring to...the degree of the effect will vary from individual to individual. The more susceptible to advertising, hype, propaganda, etc someone is, the more likely they are to internalize negative/harmful stimuli seen in media. As always, it is important to think critically about the media you consume, which of course can be a tall order for children (to say nothing of many adults). Grow up with a steady diet of anything, and it will inform your world view.
