If you know to within, say, 10 seconds how long your routine is, you can set up your cellphone with an alarm and use it as a final load so that it rings or vibrates before the reveal. If you have your watch on the table or there's a clock with a second hand visible, you can sync your phone to that to help with the timing. There are loads of gags you can use with this.

I think the watch, wallet, phone and keys direction is a good one to go in for totally impromptu loads. Some of these objects are tricky though; I guess a watch with a leather strap and keys in a key case would be helpful.

People seem to like money - Loosely balled up bills - the larger the denomination the better do work well as final loads. I have never used them for the cups and balls but have as a single final load for a chop cup.

If I know that I could be asked to do magic, I cary a small plastic case containing fie prepared playing cards that can be made to switch places when laid down. A small pack of "business" cards with an "out to lunch" routine on the back. I also carry a Pea Can. Finally I am always prepeared to to a torn and restored papeer/toilet paper/napkin trick. So to aid with those, I carry a very mini wand made from a q-tip with the fuzz cut off and blackened with a magic marker.

I remember performing in a restaurant and forgot my loads - I went into the kitchen (with the managers permission) and got three lemons.

I used them all night long and the audience never knew the difference.