I don't normally do these 'lifehack' kind of posts, and there's no danger of this turning into any kind of self-help blog.
[On occasions when I've had to talk to students and suchlike I'm inclined to respond to career advice type questions with something along the lines of 'See what I did? Don't do that'.]
The items above are ones that I carry with me for any pitch, presentation or client meeting in which I may have to show stuff on a screen.
A mini dv mac to HDMI adaptor.
When turning up at your meeting you may have to plug in to a massive TV and these days the regular PC in slot is starting to become less common.
A mini dv mac to PC adaptor.
This will be pretty familiar, you usually have to plug in to some PC contraption.
[Note: I'm fond of the Guy Kawasaki 10-20-30 rule.
10 slides, and a minimum of 30pt font.
The 20 stands for 20 minutes (this is how long you should expect to talk for in a one hour pitch or meeting).
This allows you 40 minutes to answer questions etc (expect to use about 20mins).
Guy also recommends reserving the other 20mins to set your presentation up while having to navigate the Microsoft operating system.]
Your mac remote control.
Never trust the fangled space age looking PC remotes that may be provided.
A remote is essential to allow for maximum pacing up and down, pontificating and strolling menacingly round the back of your audience like Robert DeNiro in the Untouchables.
Portable bluetooth speaker.
I've been caught out by no audio equipment too many times.
In a small boardroom type meeting you can simply whip out your speaker and place it in the middle of the table and play your videos or audio.
While there is no substitute for knowing your material inside out (this will get you through any tech problems better than any gadget) being prepared makes you at least look like you know what you are doing - a lot of the time this is half the battle.