I always add some homemade vanilla extract for a burst of vanilla flavor. Call me crazy... you won't be the first. As kids on the farm we would also put in a fresh egg.
Lou Reed wrote a song about egg cream. Selzer water and egg all shaken up or something like that ... never sounded good to me. Has any of you ever tried one of those. I'm still hankering for a shake like LT posted.
We LOVE Egg Creams. We go to Harold's New York Deli in Lyndhurst or Parsipanny and get them in tall frosty glass mugs with handles. (You can also buy the Fox's U-Bet there. I get the Fox's at Shop-Rite.) They also have Doctor Brown's Sodas. Mom used to LOVE Doctor Brown's celery soda.