If you have 4-5 guys: “I Want It That Way” by the Backstreet Boys
If you have 3-4 guys: “Greased Lightning” from the musical Grease
If you only have 2 guys: “Total Eclipse of the Heart” by Bonnie Tyler
If you are singing alone and want to rock: “Summer of '69” by Bryan Adams
If you are signing alone and want to make sure nobody looks at you the same ever again: “They’re Coming to Take Me Away, Ha Ha…!” by Napoleon XIII
In my experience, most karaoke companies have it in their database. If you can do crazy eyes and a decent falsetto, it’ll be unforgettable.