I only use the STS, Sponge balls and the No.2 Pencil in school. And maybe a card trick here or there. Mostly I don't carry gimmicks.
Most card tricks or any other effect take too long usually, and you'd want something that you can do in any situation, and that have so to say no angle difficulties.
The STS is great, but doing it more then once a week is kinda useless I think, because you don't need people going "yeah um.. like can you do that.. thing you do everyday..the shoelace thing..mh cool dude.."
But that's just getting used to it.
Sponge balls are fantastic, you can walk around doing it, you can in almost any situation pull one or two out, get some people to help you out, and do a simple routine.
I like to do them for the new students, or be casual-offensive and make a ball appear from their jacket, ear or whatever. I find it being a great icebreaker and it puts a smile on people's faces. Although I walk around on my own practicing my sleights and memorize my routines almost all the time, I try not to do so when I'm at school because people get bored if your doing one thing all the time. And they might find out what the edited your actually doing..
Sometimes I just bring a deck of cards(always have one on me but still), and just shuffle it. Brings attention when you then cut the deck in different ways, and if your sitting you can ask the person next to you to take a card, and so on.
The No.2 Pencil is a fun asset to have with you, if your about to begin class and you have 2-3 mins before the teacher comes you can take it out and do you thing haha.^
But the sponges are a definite win in my book, I had a test the other day, and took a ball out of my pocket and got bored and was almost done, and I started to mess around with it, doing the ten count while the teacher was looking at. He made me do it several times aloud and this was while I was having a test about history:D
You really don't need to be gimmicked out and have 20 different things to do. Keep it simple, few things and only if people ask you should bring out a longer routine, as most have other things to do then to watch you work your magic.(pun intended)
But you kinda feel it after a while what you need and don't need.
(The attention from the girls would be nice)
<.< >.> It's really fascinating to look at how to girls act when you know how to do magic.. It's like your a captain of a something-team but without all the running and exercising and feeling tired. Just awesome, like your better then others;D
(Oh yeah I'm not a seasoned whatever magician dude, I just say what I see and take notes of things that are useful and apply in daily life..just in case I may give off the impression that I know everything. I do that sometimes, well in fact I do it all the time. xD Bad habit)