sniffer
a sniffer to be defined as a person who frequents a bar with attractive employees and tips to much in hopes of one day hooking up with any of the waitstaff. A sniffer is a regular at an establishment only really creepy.
Your at a bar with friends and you see an old guy or girl at the bar alone trying way to hard to flirt with bartender or waitress while tipping too much to keep them intersted. As if they are "sniffing" their air hence " sniffers".