The adrenaline rush that you feel as you approach the finish line. The sound of the crowd, cheering you on. The weight of the medal being placed around your neck.
These are things I've never personally experienced. I've come close, though. And by "come close", I mean that I stood near the finish line, stealing bagels and tiny cups of water while waiting for someone else to complete a marathon. That being said, here are some races that would be really cool to attend— as a spectator. Or as a competitor. Someday. Maybe.
Bay to Breakers: This is the original weirdo marathon. House parties and concerts from local bands are scattered along the route, and runners are notorious for dressing in seriously crazy costumes- or not dressing in anything at all. Sadly, floats, alcohol, drunkenness and nudity were all banned by The Man in 2009. Stop by the festival at the finish line anyways!
Hudepohl 14k Brewery Run: The advantage of running this one is that they include a map of historic breweries that the race route takes you past. The advantage of spectating this one is that you can use this map of awesome bars to pre-game the race afterparty.
Wineglass Marathon: If beer isn't your drink of choice, talk a loved one into signing up for the Wineglass Marathon. Then while they're running, you can swipe the complimentary bottle of champagne they received in their swag bag and then relax with some bubbly. Maybe save them a celebratory sip for when they're done, though.
NYC Pizza Run: Post up near Tompkins Square Park- it's the start and finish line, so you can watch the hordes of hungry runners leave excitedly- and also watch them limp back, exhausted and stuffed full of greasy pizza.
Honolulu Marathon: You can relax on the the sand with an umbrella cocktail and, you know, not run 26.2 miles while your friends work up a sweat jogging. Bonus: the after-party is practically on the beach!