LoudMax (Free Limiter VST)

If you want a free, handy VST limiter, then Loudmax available here is a strong contender. It is a very simple yet powerful brick wall limiter with two controls. A threshold and output are all it provides for a final touch on your mastering chain. 

It is especially useful for those getting used to the idea of limiting due to its incredibly simple GUI. To use, simply drag the threshold to a point where you don't want the volume to exceed and set your output level. 

I frequently use this to end an effects chain, when the track's volume is satisfactory but there are still a few peaks clipping.

The best results that I have found are when this is used in conjunction with a compressor(s) prior to it as there is no ratio control. As such I use it more as a stray dynamic control effect as opposed to a gentle compressor.

If you are a more developed producer/engineer, this may not fully satisfy your needs but if you are doing a rough touch up or are not mastering a professional song, then it's a powerful tool.