Beta Capsule
The device used by Hayata to transform into Ultraman. He usually just raises it above his head, clicks the button, and off he goes. Kept in the left breast pocket of his Science Patrol uniform. On one occasion, Hayata tries to transform with a spoon. As far as I know, Hayata doesn't say anything when he transforms in either the Japanese or English versions, although several of you have asked.

Ultra Eye (a.k.a. "The Task Mask")
The device Dan Moroboshi and Masaki Kazamori use to transform into Ultraseven. Kept in the left breast pocket of the uniform. Dan sometimes says "DUA!" when he places them on his face. He tries to innovate poses... stretching his left arm to the side, or dropping to his knees and falling face-first onto the Eyes if they happen to be on the ground. The most stolen item in history. Melts in 'Ultraman Leo' when Seven is severely damaged by Magma-seijin and the Gillas brothers.

Force of Will
The method used by Hideki Goh to transform into Ultraman Jack. No devices necessary (thus missing out on some toy revenues). Other Ultras can use this approach on occasion, especially Ultraman Dyna. The members of Ultraman USA are also not itemized, which is probably why their pilot episode never got picked up.

Ultra Rings
The devices used by Seiji Hokuto and Yuhko Minami to tranform into Ultraman Ace. Both rings shine when the time is right to transform. Usually yelling "Ultra Touch!", Hokuto and Minami bring the rings together by jumping in the air, out of planes, off of motorcycles, and even through a video screen. After Yuhko's departure from the show in episode 28, Hokuto wears both rings and tranforms alone.

Ultra Badge
The device given to Koh-taroh Higashi by the Ultra Mother. When the badge shines, Koh-taroh yells "Taroh!" does some fancy-pants arm movents, and transforms into Ultraman Taroh. They should have been more honest and called this the Ultra Brooch. Returned to his mother in the end.

Leo Ring
The device used by Ohtori Gen, who yells "LEOOOO!!!!" really loudly, and transforms into Ultraman Leo. Why do these people insist on wearing their rings OUTside of their gloves?

Beam Flasher
The star-shaped device that Choh-ichiroh Hikari tosses high up in the air, catches, and then sticks on his forehead to become Ultraman Jonias.

Bright Stick
The Beta Capsule wannabe that Takeshi Yamato uses to transform into Ultraman 80. He does a one-two punch with his fists and reaches into his back pocket while saying "80!", raises it into the air, and makes the tip extend by pressing the button. Used to enhance his UGM Lizer gun's firepower on one occasion.

Bright Bracelet
The wrist ornament Ryohko Hoshi uses to become Yullian. Thanks again to Mr. E. Bernhard Warg for this image.

Delta Plasma
The Color Timer-shaped pendant Jack Shindo wears and uses to become Ultraman Great. Jack gingerly places it in his palm, closes his eyes, looks like he's feeling something really good inside, emits weird pulsating synthesizer noises, and emerges as Great from amidst fireworks.

Flash Prism
The device used by Kenichi Kai to become Ultraman Powered. I believe "Flash Prism" is the Japanese name for the device, which was known as the Beta Capsule in the original American version (the same name as the original Ultraman's trasnformation item).

Pikari Brusher
Electric toothbrush used by Asahi to transform into Ultraman Zearth. Because the show is a parody, I guess they really went out on a limb. At least it's consistent with his hygiene fixation.

Spark Lense
Device that brings out the light in Daigo Madoka, transforming him into Ultraman Tiga. Daigo often performs some gratuitous arm waving before transformation. Sometimes he doesn't arm wave, because, like I said, it's gratuitous. Also manipulated by Masaki Keigo in becoming Evil Tiga. Crumbles into dust at the end of the series. Ornament on top shaped like Tiga's tecter. Known as "the Torch" in the 4Kids Entertainment English dub.

Reflasher
Magical talisman that lands at Shin Asuka's feet, used to transform into Ultraman Dyna. The design looks kind of like the face of Dyna... the jewel springs open. Not always necessary for transformation, yet not enough for it either.

Esplender
Cookie-cutter-like device used by Gamu Takayama with a loud "GAIAAAA!" to become Ultraman Gaia. Contains the light that is his essence. The only item to be created by the human host... in fact, for the first few episodes, Gamu keeps the light in a silver cylindrical container, which looks suspiciously like a lipstick container.

Agulator
A bracelet that spins, springs open and emits a blue ray upward that makes Hiroya Fujimiya transform into Ultraman Agul, after shouting 'Agul!' (or AGULUUU!, to be more accurate). The centerpiece looks like Agul's Life Gauge.

Nice Dreamer
A wrist watch that contains chocolate balls which is what Ginga Yumeboshi eats to become Ultraman Nice. Probably why Ginga is one of the larger human hosts, other than latter-day Dan Moroboshi. Notice how Nice's Color Timer is worked into the design. Very nice touch.

Estraller
The device that Genki Kagura uses to become Ultraman Neos. What is this supposed to be, a paperweight?

Cosmo Pluck
The device that transforms Musashi Haruno into Ultraman Cosmos. trasparent bulb-like tip springs open.

Trivia

Interestingly, it looks like Tsuburaya Productions didn't keep the old transformation items around after they were done producing the first few series. In 'Ultraman Taroh', episodes 33-34, Ultraman, Ultraseven, Ultraman Jack, and Ultraman Ace all return and transform on numerous occasions. You can tell that they don't have the old items around anymore because they keep faking it with bright lights.

Which makes me wonder... maybe Hideki Goh makes cameos in every series through 'Ultraman Leo' because he never required an item to transform?