I've had quite a few, but the worst one was probably when I celebrated my 24th birthday in Manila.

We were doing "funnels" of beer, but unbeknown to me, my "mates" had laced mine with shots of tequila and pepper sauce! It went down, but came up again 5 minutes later in the gutter outside of the bar!!! I was lying on the floor feeling awful and they were all standing around eating fish balls and laughing at the puking kano!