Cell
Cell is a powerful amalgamation of genes taken from numerous fighters. His DNA has elements of Goku, Frieza, Tien, Piccolo, and many others.
How to Get Him
I believe that he is running loose from the Super Android #17 saga. He could be convinced to join.
Starting Level:
65; power level of 34,000,000. He has great technique, but appears quite unprofessional.
Abilities:
Create Cell Jr.: Cell can create numerous Cell Jr.'s. These small, blue versions of his Perfect form are quite formidable. Their power level is hard to pin down. They easily defeat all of the Z Fighters, even Piccolo and the Super Saiyans (with power levels about 15,000,000). However, Gohan with his whopping 27,000,000, easily defeats the Cell Jrs (many in a single blow)!
Destructo-Disc: Although we don't get to see Cell using this move (I believe), one of the Cell Jr.'s uses it on Gohan, who easily evades it. Cell inherited it from Krillin. The Destructo-Disc is a disc-shaped energy attack that is quite lethal.
Instant Transmission: Cell learns Instant Transmission from Goku after the self-destruct that kills Goku. Instant Transmission is basically a "true" teleport: a instant movement from one location, say King Kai's to Earth, in mere moments.
Kamehameha: Cell uses Kamehameha quite judiciously, as well as his Cell Jr's. Kamehameha is the energy blast utilized by Gohan, Goku and Krillin. It involves a long charging period during which the user yells the words a syllable at a time. The user then launches a ball-shaped blast at his opponent. Kamehameha appears to be remote controlled.
Life Drain: Cell's tail enables him to absorb power from his enemies. A major advantage over similar power-absorbing Androids is that he can absorb some of the DNA/lifeforce as well. If he absorbs a significantly different life force (the Androids, say) then he has in his collection, his powers increase greatly.
Regeneration: Perhaps Cell's most fearsome ability is his awesome regeneration, capable of bringing him back from a single complete cell!
Self-Destruct: Cell probably inherited this from Chaotsu. He has the ability to swell up like a balloon and explode, destroying enemies much stronger than him.
Solar Flare: Cell uses Solar Flare twice: once to evade Piccolo's Super Namek powers, the second to distract Android #18 for the kill.
Special Beam Cannon: Again, Cell apparently never uses Special Beam Cannon on his own, but one of his Cell Jr.'s uses it on Gohan in a vain attempt to stop him. Special Beam Cannon is a powerful move utilized by Piccolo. It is a red-shaped energy blast with rings going around it at equidistant intervals. The rings offer a multi-attack feature. Special Beam Cannon is what is used to kill Raditz in the first few Dragon Ball Z episodes.
Spirit Bomb: Cell brags about being able to use the Spirit Bomb, but he never does utilize it. However, it does belong in his bag of tricks.
Split Form Technique: A technique utilized by Tien and Piccolo, Split Form involves splitting up into 2-4 different bodies and attacking the enemies. Cell pulls it out of his bag of tricks in a battle against Goku.
Square Blast: Tien's move, a move used to stop Cell from absorbing #18 early on, is a powerful kinetic shock in a square shape. Two Cell Jr's utilize it simultaneously in the attack upon Gohan.