Pre-MK I used Lancome Definicils. I really loved it.
I haven't made it to a Lacome counter since I sent all of my MK crap back, but Allure recommended Cover Girl Lash Exact. It comes in a purple tube and instead of hair bristles, the brush is a rubber/neoprene/plastic material. I'm really loving it. It separates my lashes really well, and NO CLUMPS!
I think, when I need any, I will be trying the cover girl! Right now I don't need anything, I might as well finish up what I have!