I usually go with a transpo that involves a visual color change or one that happens in the spectators hands if I start with cards. If I don't start with cards I almost always do Digital Dissolve. That's just what has worked for me.
Personally I, 95% of the time, never start with cards. My reason is because cards, while common, are not something people carry around regularly. Usually I will start by introducing myself not as a magician but as a normal person then once I am actively having a conversation with people I'll try to steer the conversation to my opener which is usually "Crazy man's handcuffs" followed by Marcus Eddie's "Stairway". I'll let them react then go with the flow from there and do like one or two more things but I always leave them wanting more. I try to use magic to express who I am, not let it define me.
I know the OP was just looking to get some tricks out of his question but more tricks is the last thing you want if you want to be a halfway decent entertainer.
If there is a table, I like to do Joshua Jay's poker opener. It is what he calls a fireworks magic trick because of the multiple magical moments in it and you can save interaction with the spectator for later once you have your reputation established because the spectator doesn't pick a card. I also like to do 2 card monte or a selected card reveal from either a force or a colour change. Also, if you want to carry red and blue cards with you, Oz Pearlman's blindsided is a pretty cool trick to keep in mind. If you're doing a magic show (though this could work for street magic) Thumbstruck by Joshua Jay is a trick that is a gag and magic trick combined which makes for a good icebreaker and opening trick. (These are all card tricks so if you want to do a coin trick or something that's fine too.)