You have your DSLR. You have your lenses. Many of them. What do you do if you really don't want to take them ALL with you?
Well, there are things to consider - how much weight you are prepared to carry and what compromises you are ready to take.
My personal choice for ultra light traveling is taking a wide to telephoto lens (for universality) and a small fixed focal for bokeh and its light. So, in two lenses you have almost all you need.
My set : Tamron 18-250 and 50mm f1.7 (which, by the way, is so small I can carry it in my pocket literally).
Of course I wish I could have more lenses with me at times, but when you need to go light - that's what I recommend.