Hobo's Suggestions :)

[DaHoboAtWalMart]

1. 'Teamwork' function.
- Very simply way of adding more happiness to the game. If two or more colonists are doing the same thing, they get a small bonus for each person doing it. So, each colonist might get +2 or more happiness for each person working on the same order, but colonists doing other things won't be affected.

2. Sun lamps dry mud.
- Quickens the process of making mud into dirt. Perhaps an alternative to fertilizers.

3. Cleansing robots (Roombas!).
- Go around rooms cleaning like a Roomba. Perhaps makes humming noise that slightly annoys colonists. Needs charging station?

4. 'Leisure' function.
- Idling colonists get a small happiness boost.

5. Narcotics.
- Damages/sickens colonists perhaps, but makes them much happier. Expensive way of easily and quickly stopping insanity, or giving damage, speed, etc. buffs. Different types of narcotics do different amounts of damage, have different time periods for mental healing, different growing requirements (may need hydroponics for some), and addiction/withdrawal. Addiction needs riddance by doctoring. If a colonist runs out of supply, or you want them to quit without doctoring, they face withdrawal symptoms, which mentally and physically damage them. Perhaps minor drugs have less or no addiction.

6. Narcotics traders (Heisenberg Inc.!).
- Self explanatory.

7. Alcohol.
- Impairs ability to do work. Temporarily grants 'trigger happy' trait.

8. Gym rooms/rec. yards.
- With a multipurpose work equipment block, which allows colonists to periodically heal old wounds or gain melee ability.

9. Shooting range.
- Shooting equivalent of gym. Allows colonists to gain shooting ability. No more having to hunt every animal in sight (besides for food).

10. Plant Genetic Modifications (added 11/15/14)
- I'm not sure how many times this has been mentioned, but I heard @JimmyAgnt007 toss the idea into a thread some minutes ago and decided to expand upon it.

The rimworld plants could be genetically modified variants to produce rapid foods

This concept sounds great to me. After all, we can give people bionic limbs, right? What I think, is that you should be able to buy all sorts of genetic modifications from food traders. Food traders are pretty useless as of now anyway; they're only really helpful when your colonists are starving, and they rarely even come at those points anyway. All the aforementioned gen mods should have their own (perhaps) pros and cons. Maybe you could get a mod to stop crops from being affected by blights, but in turn makes the crop take slightly longer to grow. Or, maybe you can get any type of growth speeding mods, from 1.5x to 5x speed, but the faster they grow, the more prone they are to blights. Furthermore, the more helpful a mod is without causing too much side effects, the more expensive/rare it should be. Oh, and while we're on the topic, pests/pesticides (more realistic than a blight every two weeks, I feel)?

Wot do you guys think? Perhaps I went overboard on the narcotics. 
May add more at some point.
Sorry if any of these have already been mentioned, I'm sure a couple have.

[skullywag]

9. Theres a mod for that. Adds an indestructable target colonist can force fire on and gain xp.

https://ludeon.com/forums/index.php?topic=2158.0

[Sir]

I'm a fan of all of these, especially #3 & #4. Massive +1
Good suggestions.

[ZephyrSly]

1. 'Teamwork' function.

Actually, I think thats how the 'social chat' mood effect works, though still a good idea.

4. 'Leisure' function.
- Idling colonists get a small happiness boost.

Now this! Honestly, the amount of times I've had twenty idle colonists! And all they do is loiter...

The rest of the ideas I really like actually!
Also, it'd be pretty cool with addiction if your colonist would constantly try to get drunk or high, and end up being more of a nuisance then a help to the colony.

[skullywag]

If colonists are idle it really means they have no job to do. If you have a table click on it, youll see a meeting place setting. Make sure its on and your colonists will gather and chat when idle gaining mood boosts.

[ZephyrSly]

If colonists are idle it really means they have no job to do. If you have a table click on it, youll see a meeting place setting. Make sure its on and your colonists will gather and chat when idle gaining mood boosts.

Huh didn't know that, though my colonists have never done that... odd...

[skullywag]

Its on by default so if you have more than 1 table turn the others off.

[ZephyrSly]

Thanks Skullywag

[keylocke]

Heisenberg inc ftw! 

[kingtyris]

Good ideas. I especially liked the workout room idea.

[StatikMilk30]

Something you can do for addicted colonist is that you can put them in prison until they calm their addicted tits.