You never know what kind of trouble you might run into on a particular night, so keeping an array of accessories in your bag in addition to your balls and shoes is always a good idea. There is a lot of stuff out there, but I've compiled a list of what I keep in my bag so that I am prepared for just about any occasion.
Other than giving you something to play with while waiting for your ball or the bowler on the next lane to finish up, the bowling towel is probably one of the most important accessories in my bag. Before each frame, if not each ball, wipe off the surface of your ball to clean away all of the oil picked up during the previous frame. There are a lot of variables in bowling, so by removing this residue build-up you can at least be sure that your ball surface has not changed from frame to frame.
Whether you realize it or not, your thumb and fingers expand and contract based on the weather. When it is hot and humid, your phalanges will expand. When it is cold, they will shrink. In a 30+ week league season in the majority of the country you will experience both extremes. This same phenomenon can occur as the bowling night progresses and your thumb can swell from the first to the third game, so it is a good idea to be prepared to make a quick change on the fly.
Throughout the majority of the season, the thumb hole on my ball is a little too large. I use one to a few pieces of black electrical tape to give my thumb a snug, but comfortable fit making sure that the thumb can easily come out as I release the ball. Black electrical tape and the pre-cut bowler's tape is pretty much the same thing, only a roll of electrical tape is a bit cheaper. When adding tape to the hole, be sure that the edges are even or below the ball surface. Also, only apply tape to the part of the thumb hole that touches the back of your thumb. This will allow you to make adjustments without affecting your span.
If you find that your thumb has swollen to the point where the ball is sticking at the release and all tape has been removed from the hole, the only option is to expand the hole. A few swipes with a piece of sandpaper or an emery board will allow you to make a slight adjustment to the hole size without affecting the overall quality of the original drilling. As with tape, try to avoid changing the front half of the hole so you do not change the span and sizing on the ball. It is also important to keep in mind that while tape can be removed or added to a hole, sanding is a permanent change. So be careful and only sand enough to get you through the night.
New Skin/Skin Patch
If you have ever tried to bowl with a cut on your thumb or finger, you know how painful and frustrating that can be. You also know that a Band-Aid just doesn't cut it. A skin patch or some New Skin applied over a small cut or an area that sees a lot of friction during the course of the night will allow you to bowl without much of the discomfort. However, be warned that this will probably sting when initially applied to a cut, but once it is on and dry you can barely tell its there.
Ball Cleaner/Rubbing Alcohol
Before I touch on this one, I will say please check with your league officials regarding the rules on changing your ball surface during or between games. Many leagues will not allow ball cleaner to be used once league games have started.
That being said, a ball cleaner will allow you to get a little more bite on the lanes, particularly in high oil. A bowling ball surface, much like your skin, has pores. These pores, among other things, allow your ball to hook on the lanes. And also like your skin, a build-up of oil can clog those pores, preventing them from doing their job. To avoid this, use a ball cleaner or rubbing alcohol at the end of a particularly oily evening or before practice. If you arrive early enough to the alley, watch how others' balls react on the lane. If they seem to be sliding or not grabbing, take that as a sign that it might be a good night to clean the ball.
One of the most frustrating things a bowler can encounter is a less than pristine approach. If your sliding foot is sticking at the line and throwing off your shot, a few pats of a rosin bag on the bottom of your sliding shoe should allow for a cleaner follow through.
Also, if your thumb or fingers are wet or sticking in the ball, a little rosin will absorb the moisture on your hand and should help your release.
I find that it usually helps to keep a pocket knife or a small pair of scissors in your bag to cut tape and help place it in the ball. Plus, you never know when these might come in handy.
Its also never a bad idea to keep some cash and bowling coupons in your bag, for impromptu raffles, brackets, 50/50s and practice sessions.
What do you keep in your bag? Is there a bowling accessory you couldn't live without?