I used dmenu as my main application launcher for a few years. I switched to Mac a few years ago and still miss dmenu and dwm (or just tiling window managers, in general). Could just be rose-tinted glasses, however.
Anyone who hasn't seen suckless.org (where dmenu comes from) should look through what's on there. It has some really small and often useful tools.
You can configure what Spotlight indexes. I turn off a lot of it so that it doesn't suddenly use a bunch of CPU indexing things that I don't care about.