Guinness would be my answer. Guinness gets bashed on this site all the time for being weak, watery, and so forth, and while that is certainly true when compared to imperial stouts, you have to take it for what it is. It's an Irish dry stout--it's meant to be very light and sessionable. It's extremely smooth and creamy, and even though it doesn't have much flavor, it's still very enjoyable and you can drink a ton of them in a row without getting super wasted. Haha.