It's hard to beat

  cmd+space safari

Agree, but it's actually more like:

    cmd+space sa <return>

For most people. Because it seems to prioritise based on frequency of past selection.

Except that the first one is supported by TAB-completion.

With the right zsh plugin, either of them will tab complete properly. (I think "osx" from oh-my-zsh is the one that does it on mine)

Edit: looks like this is actually built into zsh. Slightly surprised, but just goes to show I know almost nothing about the shell I use every day.

Yes but I use the default bash, as do probably most OS X users.

Check out Alfred[1] it supports tab completion.

[1]http://www.alfredapp.com/

The -a flag is also great to open a file in a specific app, e.g. `open -a Safari logo.svg` or `open -a Marked README.md`.