a few good ones are the hurricane, gin sour, whiskey sour, tequila sunrise (not that strong i think, but it's pretty good), margaritas, kamakazee, tom collins, and long island iced tea.
you could always make a sangria, that shit can be made so strong and still taste so good.
really anything you make, you control the amount of alcohol put in it.  so really its all up to you what you make into the strongest drink, unless you're at the bar, then i recommend the kamakazee or long island.  that shit will mess you up.