What fun and low-cost fringe benefits/perks would you offer to employees?

As a company, you mustn't be too generous, it's enough just not to annoy your employees (even that is usually too much to ask for).

If i see the big list of things some of you have/promise: Think about the time when your company (luckily?) gets "grown up", and inadvertantly all those things get cut by some new managers: People are REALLY pissed. It's harder to have a loss than never having had that thing...

Happened in our company: big fights when the free orange juice went away. Btw, I dimly remember was some Dilbert saying: If they cut down free drinks, you better run... It was right, shortly after the drinks most of the fun was cut too.

I work for a mid sized company, but our CIO has autonomy to run his department how he sees fit. The backing of the CFO is so that, he has cash to give us some great unofficial benefits.

1. The all important and wonderful flex time. As a few others said "were adults, leave us alone"
2. We don't get regular lunches, but 4-5 times a year our whole department (probably 20 people total including support) get treated to a lavish lunch of some sort. Sometimes we take over a nice restaurant, last one was Brazillian barbecue, or have high quality catering brought in. These lunches take a couple hours and we all just hang out and have fun, getting paid of course, even our hourly people. Plus a few times a year the individual teams within the department go out to lunch on the company's dime.
3. We celebrate pirate day. Some of the department dress up like pirates and we have a huge catered lunch and we give prizes for the best pirate name. Last year I won $100 in itunes gift cards. This may sound dorky and hokey to some people, but it grew organically out of our department's own ideas and by and large, technical people are dorky so it fits :)
4. Game day. This is fantastic, every year for one work day between Christmas day and new years, we all come in to work but we play games together all day and are fed breakfast and lunch. This is like a lan-party at work using our company's uber network and servers. The morale boosting power of this one day cannot be overstated. We talk about it for months in advance and for months afterwards. All it costs is 1 day of pay and our entire department is giddy with excitement. It's genius.

These are just a few of the perks I can think of, but they are the most "obvious". Basically I see it as our CIO knows his people, and has created things tailor made just for them. Creative benefits are not universal. I doubt a department full of accountants would be all that thrilled with game day :) but we LOVE IT!

Finally, nothing can replace a good boss. This one is tricky, though, because a good boss means something different to each employee.

Forgot to mention one thing. Get rid of under performers immediately. Few things aggravate a good employee more than a bad employee.

On the lunch thing, you underestimate the pressure to attend on those who have other obligations or who have a life outside of work. And on the unmetered PTO thing, the pressure is likely to take small vacations, if at all - in my experience (observing from outside as I've not been in that environment yet), people rarely take as much PTO as they would in a situation in which it was accounted for - due to peer pressure or the fact that there just never, gosh darn it, seems to be a good enough time for 2 weeks off.

You asked for cheap, and the answer is surprising, at least to me: it may be that the most important hire is your least expensive hire. The best places I've worked had one employee that the less than the best did not: an outstanding HR person. This is probably the lowest paid professional in the entire startup or small company and yet it's the person who makes the technical folks most excited about work in general. Technical folks are often poor at planning group activities or seeing the utility of them. However, a single great HR hire pays massive dividends in employees' enthusiasm and the company's responsiveness. If given 20 great technical people and no "culture" person (say, just some random admin person) versus 19 technical folks and 1 great culture person, I'd choose the latter. I might gain the productivity equivalent of 2-5 more people in the process.

I realize that this isn't a standard "fringe benefit", but it's great to have coworkers who are having fun. The great "culture" person will put together events, such as birthday celebrations, movie outings, and more, plus keep the management considerate of employees who have personal issues to attend to, such as funerals, sick relatives, etc. For instance, when an employee has a death in the family, a considerate company will be sure that flowers are sent to the funeral. Trust me, an employee will never forget that consideration. So, treat your people well, and hire people that know how to do that.

Disclaimer: I'm not an HR person, I'm in the technical crowd.

Set some limits (maybe $$?), but let them tell you what they want. I don't find things being the same for everyone as equal, fair, etc. Maybe on a regular basis, everyone can pick from a list, a "Get out of Jail Free" card. Instead of getting to leave early on Friday, I may choose to have one extra vacation day. We often jump the gun and think people will take advantage of this and work the system, but that is because so many companies are not taking your approach by wanting to do something good for the employees. Don't offer me a cupcake and then stick your finger in the icing before handing it to me.

First, never assume that as startup it ok not to offer market-rate salaries to our employees. If you go that way you will never recruit the team you need to succeed. Remember, execution is the key to success.

Second, just introduce perks based on what your team wants. You don't need to ask on internet about that.

A flexible working schedule and nothing else. Pay them enough they can afford what they want (gym card, car, whatever).

Would you think that a chess player will be happy with your gym card? Or that a bike racer will fall for your BMW?

Pick up a Wii with a copy of Tiger Woods Golf and Beatles Rock Band

More than snacks, lunch. It's not as expensive as it sounds (people don't expect sushi), you can leave Friday out of it (Fridays everyone goes to lunch out), and bringing lunch in actually cuts a lot of wasted time out of the day without anyone feeling like they're working more.