I have bundles ultisnips and youcompleteme installed on my macvim.
The problem is that ultisnips doesn\'t work because tab is bound by ycm.
I tried putting let g:UltiS
While Many answer works fine in this post, I just want to say that the problem is caused by key binding collision between YCM and UltiSnip, while YCM support UltiSnip snippets by default, it takes the default UltiSnip expand trigger as its completion select key, so UltiSnip snippets will not be expaned by . Give them different key binding will solve the problem, I personally use for YCM and use the default for UltiSnip. You can get more details with help youcompleteme doc in vim.