Since Maniac Mansion was the one that started it all for me when it came out on the C64, the choice is rather clear. :angel:
Of course most of the later games were even funnier, deeper, had better graphics and sound etc. but only MM will forever have this special place in my heart (shortly followed by Zak, of course... ah yeah, the memories of a wasted youth... LOL

).
But I gotta admit that I never before and never again laughed as hard or as much during any game then I did when playing "Sam & Max"...