Probably his biggest contribution was getting infected by cells from Species 8472 giving The Doctor plenty of samples with which to experiment and find a way to fight the aliens from fluidic space. Still, all he did was lay on the bed the whole time.
- He claimed he remembers being in his mother's womb.
- He once thought a '36 Ford truck might be an early hover-car and didn't have a clue who Amelia Earhart was.
- He got stuck in an alternate dimension and the only way he can find his way back is to get himself killed.
- He was once suspected of being a Maquis sympathizer (in an alternate reality) on Earth and they put a tracer around his ankle. Naturally, Harry later tries to remove it and leaves the job half done when his girlfriend comes to talk to him, thus ensuring the alarm will go off and the authorities will be there in seconds.
- An alien race infected Harry with a virus and convinced him he was really a member of their race. This race apparently reproduces by extracting DNA from the males to produce children. The male is killed in the process. (I guess people in Star Trek don't realize that DNA replicates itself--that you only need a few cells which certainly is not lethal. We can mass-produce DNA today)
- He preferred to return to Voyager and be stuck in the Delta Quadrant than remain on Earth in an alternate reality with his horny girl friend. He would even rather hang out in a pool hall with Tom Paris than be with said woman.
- He turned down a double date so he could continue running diagnostics.
- He once entered a virtual reality computer simulation to investigate why some aliens remained inside their stasis chambers. We get a good look into Harry's mind as the computer simulation reflects the person's thoughts. And what do we see? A burly, harry, bare-chested man dressed in leather chopping a log in half with a pink guillotine.
But no, he's not supposed to be gay.