One of the best supplements one can take for a variety of goals, protein powder helps the body build things like muscle and tendons. When used appropriately, protein powder can help one lose a substantial amount of fat and gain an equal amount of muscle. I take a protein powder that has zero carbs and includes a variety of vitamins and minerals (a bit more expensive, but worth it).
Also a great supplement, creatine is used for those doing weight lifting (generally). Through a complicated process involving adenosine triphosphate (ATP), creatine helps your muscles hit more reps with a higher weight. In essence, it helps you lift a few more reps. Some studies have suggested that long-term use of creatine in lab rats with liver disease caused liver failure, so be wise when using this. It's generally suggested to cycle on and off creatine.
Caffeine is another supplement I take regularly to help me burn a bit more calories throughout the day (when paired with ephedrine). It's easy to take too much caffeine, so start off slow. You can take caffeine in drink form (generally with coffee or energy drinks), pills or powder. When wisely paired with ephedrine, it works wonders on fat loss. But again, DO NOT pair caffeine and ephedrine if you're a first time user. Do your research. I am not responsible for any dumb mistakes anyone makes because of lack of research.
Generally these are not worth the money. SOME multi-vitamin companies may actually have some worthy pills, but I haven't seen any yet (apart from USANA). If you are eating a good range of different foods, you're probably getting all the vitamins and minerals you need (as long as you don't suffer from some disease that makes you deficient in something).
Another great supplement to take while on a diet of any sort. Omega-3 oils help with all kinds of things, especially losing fat. There is definitely undiscovered potential with fish oils!
Raspberry (or any) ketones
Definitely not worth it. This works off the premise that if you are in ketosis (your body is producing ketones because you are on a low carb diet), you'll lose more weight. Check out Lyle's analysis of whether or not ketosis allows one to lose more weight versus a low fat diet here.
Currently I am taking the following;
-flax seed oil (omega-3 source)
The reasons I'm taking these 4 supplements;
1. I've done my research on the side-effects of any of these supplements both individually and in combination with each other
2. My goal is to lose weight
3. I'm an experienced dieter
Obviously one can spend thousand$ of dollar$ on supplements if one doesn't do their research. There are only a few supplements that have shown their worth through several studies; creatine, protein powder, caffeine/ephedrine. I'd be hard pressed to find research to back up taking anything more than that.
DO NOT take any of the supplements mentioned above before doing adequate research on them and deciding on your own if they will assist you in your goals. I do not advocate the use of any of the supplements mentioned here.