When playing speed chess, the element of surprise is obviously much more important than when playing longer games. Another important factor is knowing the positions you will be playing before the game starts because chances are you won't have much time to contemplate. Due to these two facets of speed games, many chess players chose to alter their openings to better suit the time control.
Ideally, a blitz or bullet chess opening is somewhat irregular, has a similar move order no matter what your opponent plays (so you can play the moves quickly), and is tactically resistant while still offering attacking chances for the player.
I have found that these criteria are all met in the Colle-Zukertort.
This opening is relatively easy to play once you understand the key ideas (the move order stays pretty much the same no matter what your opponent does so you don't have to learn too much theory) and it offers prospects of a fierce attack on the king.
Helpful resources on the opening:
Also good for blitz (or longer games for that matter) is the Colle-Phoenix Attack, based on a similar set up for white.
If you have any ideas for tricky blitz openings, please comment and share or post on my forum: Blitz/Bullet Chess Openings.