What would everyones opinions on the 'must have' comics be?

Which storylines your favourite(s) or considered great due the importance of the story contained within?

As a long time comic collector it is suprising that I really don't have much in the way of Transformer comics. What I do have I enjoy and would like to add to, especially considering some of the artwork and stories I have seen in previews.

My only concern is that there is a fair bit out there and to begin with I would like to concentrate on the more 'essential' to continueum (sp?) or mind blowingly good stuff.

Oh and this is in reference to the more recent stuff as I am not so interested in the older stuff since I have or have read alot of that stuff already.