As some of you may know, I love all bits: they are one of my favorite pieces of tack for ponyplay. There are a few types that I especially love, whether for aesthetics or simply the control they can exert over me. I picked a few of the less common (though still inexpensive) ones to share with you.
Closed Spoon Tongue Bit The sides of the bit (where they will rest on the pony's teeth) can be coated with vetwrap to reduce the likelihood of chipping teeth. When I wear this bit, I leave the spoon portion, which rests on the tongue, as-is becuase I have not found this portion to be in contact with my teeth during normal use. From personal experience, I find this bit to be a milder, albeit more aesthetically appealing, alternative to a bit gag with rubber tongue port. Most tack stores sell this bit (I purchased mine from Bit of Britain).
The Chifney Anti-Rearing Bit Designed as an in hand bit to prevent rearing, the curved mouthpiece version presses into the bottom of the pony's mouth. Thus attempts to rear (or a simple downward tug of the reins or lead line) causes the mouthpiece to dig further into the tongue and bottom of the mouth. A rubber coated straight mouthpiece version is available which is a little more mild and would be easier on the human pony's mouth and dental work. The curved mouthpiece, straight mouthpiece, and rubber coated straight mouthpiece are widely available from tack shops. I like the look of this bit thought I have not seen it on many human ponies (see a bio-horse wearing a Chifney bit).
Dexter Ring Bit It has two mouthpieces: the ring and a standard mouthpiece (typically a jointed snaffle). Aside from the additional control of the pony's head, the ring is also a nice place to clip a lead line when leading a tacked up (and possibly mounted) pony. The primary mouthpiece can be anything from a happy mouth to a spoon (Dexter spoon ring bit).
Horseshoe Stallion Bit Primarily used for showing stallions in hand, I just think this bit looks really cool. Again, this bit is fairly widely available (e.g. from Amazon).
Western Bits with High Ports Bits for finished western horses can have really high ports (even without rein action these mouthpieces will dig into the soft palate unless a pony's head carriage is correct). I love these types of bits because they reach far back into the mouth and require me to constantly hold my head in the perfect position to prevent them from digging into either my soft palate or my tongue. Some of these show bits can be expensive (often elaborately engraved with silver finishes), but you can find severe spade mouths that are reasonably priced (e.g. the ball jointed spade bit, which has a 3½ inch tall spade - this will extend well over 4 inches into the mouth when the bit is properly (and snugly) situated with the bar behind the front teeth).