I like my Moser Rex pair; they're very quiet and most horses accept them easily, I've even done a full clip on a neurotic TB that used to be doped to do so they're tough! (they're corded though, don't know if that makes a difference to you.
For just small jobs (i.e trimming around the ears and light feathers) I use Liveryman Flair Rechargable trimmers, and they're great, have really lasted on me and are small and handy to use
I have some Wahl clippers, the pro rechargeable ones, i think they're pretty good. Bought them for my horse two years ago who hated being clipped and would try to attack anyone who went near him with a set of clippers! But as these ones are quiet, small, don't vibrate much and have no cord he gradually got used to them and gradually allowed me to clip him with them. He has since been fully clipped about six times with them! (He is a thick coated cob so needed clipping all year round). The blades do get quite hot so i would buy two, then you can swap them every 15 minutes to let one set cool off and so you can keep on clipping. I feel i've definately got my money out of these clippers. They're also lightweight so your hand doesn't get tired holding them! They do work best if you wash the horses coat first, they will struggle if it's greasy, and they have more power if plugged in but work perfectly well cordless, just take a bit longer. The blades aren't as wide as normal clippers so if you want to do a full clip they'll take longer but if only for trimming then small baldes are ideal.
Mine are getting worn out now but i don't mind as thanks to them my horse is now good enough to do with normal clippers.
I've had my Walh Pro's for about 6 years - think they are just on their last legs now but have done everything from blanket clip on a wussy 16.2 to wire haired cobs feathers on a regular basis