Passionate data finder and friend-of-the-site Seth Kadish has made two charts based on one year of Las Vegas gaming data, first published on his excellent blog, Vizual Statistix. The weekly average values were derived from one year of data for all non-restricted locations in the Las Vegas Strip area via the Nevada State Gaming Control Board Gaming Commission.
Kadish found that people lost the most money at table games, in particular 3-card poker, where gamblers lost an average of 32.5% of their bets.
If you do want to head to the tables, bingo (where the house only takes 8.8% of wagers) and blackjack (11.1%) are your safest choices.
Your best bet entirely for losing the least money are the slot machines, particularly $100 dollar slots where the house only takes 3.6%, followed by the $25 dollar and $5 dollar slots.
Sports betting is pretty safe as well. Betting on baseball will give you slightly better odds than basketball or football, but sports parlay cards are super risky with gamblers losing almost 40% of their money.
So the next time you're in Vegas, remember where the smart money is and stick to the games closest to the X-axis.