M.M.
Neither of my kids are/were giggler's as babies.
My son didn't laugh outloud (very smiley, no laughing though) until he was about 9-10mos.
My daughter, who's 7mos old now, has never giggled either. Lots of smiles, but no real laughs and definitely no giggles.
Both are right on track with everything else. DS giggles up a storm and is super happy now (he's 3), and DD just started crawling at 7mos.
Some kids just aren't giggly!