In a nutshell
Cell is an oddball character who possesses some very peculiar strengths. He can be described as a slow but powerful zoning type. All of his specials do a lot of damage, he has the most projectile attacks in the game, and he has a unique 1 frame command grab that reaches full-screen, with a catch. Cell also has the fastest ground normal in the game in the form of his low-hitting cr.B, which by itself can create unblockable situations from any blocked jump-in, among other things. Tools like these give Cell the ability to force the opponent into action, at the expense of being quite vulnerable himself when cornered. Good choice for players who enjoy themselves some zoning mixed in with bizarre shenanigans.
Close st.Y - Average looking punch to the ribs. Slow startup and lots of pushback on hit, so you wont be using this for combos very often. Does have very good active frames though, so can be used as a close range anti-hop poke.
Close st.B - Quick knee to the face. One of the fastest close st.Bs in the game, used mostly for hitconfirms into launcher.
Far st.Y - Cell throws a nice right hook punch. Fairly useless, far st.B is the better poke in most circumstances, although because Cell is so tall this can occasionally stuff hops.
Far st.B - A straight, outstretched forward kick. Cell's best midrange ground poke, this has very long range and is relatively fast for what it is. Cancel it into B+Y on block to significantly reduce its recovery time.
cr.Y - Cell kinda flicks upwards. Can't be special cancelled. This move is unique in that it can actually hit behind Cell, so if you manage to dash under a jumping opponent and hit them with cr.Y without turning around, you can convert it into an easy stun combo by infinitely chaining it into itself. Not much good for anything else though, since you have the all-powerful cr.B.
cr.B - Low shin kick. Hits low. Can be special cancelled but not normal cancelled. Amazingly fast low and +3 on block, Cell's cr.B is actually so fast that it has magical powers. For starters, this move is faster than the time it takes to switch from blocking high to blocking low, so if the opponent blocks one of your jumping normals and you then land and chain directly into this, they can't block it. From there you can cancel this straight into Rushing Suki Combo for over a hundred unblockable damage. Not only that, but the startup frames of this move also last exactly the same amount of time as wake-up invincibility, so assuming you time it correctly, cr.B on wakeup will always trade with perfect grounded meaties. Very important tool for Cell. All hail the cr.B.
j.Y - Jumping hammer fist attack. Special cancellable. Slower startup than most jumping normals, and the hitbox is kinda awkward to utilize properly. In most cases, stick to j.B.
j.B - Cell wins "Most Awkward Jumping Kick of the Year, 1996". Go-to jumping normal. Decent, all-purpose hitbox, nice active frames, gets the job done. It is 2 frames slower than the fastest jumping normals in the game, but it's the best Cell has.
Rushing Suki Combo - Y - Cell rushes forward with a series of punches. Knocks down. Most damaging special move in the game at 95 base damage. Used almost exclusively for hitconfirms from cr.B. Throw punishable on block and very easy to guard counter, so try to make sure it hits.
Diagonal Ki Flame - Y - Cell anti-airs with fire. Level 1 projectile. Knocks down. Great anti-air hitbox with decent startup, but very bad recovery time. Although you may struggle to react to hops with this, it works well against full jumps, and reaches about half screen. Just don't ever use it pre-emptively.
Psychic Lift - Y - Cell uses MIND POWERS to lift his opponent and poke them. 1 frame command grab. Can hit the opponent from anywhere on the screen. Only works against opponents who are in idle standing or crouching positions. Cannot hit opponents who are in blocking animation. When used at round start, if timed as soon as possible, this command throw is completely inescapable by the entire cast. Afterwards, you can follow up with Cell Junior Attack for guaranteed oki and momentum. Learning the timing for this is extremely important for Cell players, as without it, Cell's poor movement speed can cause him to get bullied by the faster characters early on. Unfortunately, this is not a game where people remain in idle stance for long, so besides round start, you will struggle to land this against non-charge characters. Ironically, the best time to use this move outside of round start is when you are up close threatening with normals, because that's the only time people would ever have a reason to sit perfectly still against Cell. Has no throw whiff animation, so if the opponent can't be hit by it, st.Y will come out instead.
Energy Burst - B - Cell explodes with energy all around him. Launches on hit. Not very useful. Slow, bad range and very punishable on block. It does launch on hit, but because of the long recovery it must hit the opponent pretty high up in the air to convert into a combo. Still, it does hit all around Cell, making it a viable but very situational anti-air.
Negative Arrow - Y while in the air - Cell shoots his Gohan Buster down forward. Knocks down. Excellent zoning tool. It's fast, covers the perfect angle and is great at establishing space and playing keep-away. Added bonus is that it costs no health to perform. Cell maintains his jumping momentum when using this, so it's never really a good idea to use it on forward jumps.
Cell Junior Attack - B - Cell releases a baby that hops toward the opponent. Knocks down. Long startup but almost instant recovery, making it perfect for okizeme. Whenever you score a knockdown, release one of these and either follow behind it for some imposing pressure, or hang back and zone some more.
Kantsu Energy Dan - A - Cell fires a dense energy blast from his hand. Level 3 projectile. Costs 5 health to use. Knocks down. Very strong fireball, as it will plow through all level 1 and 2 projectiles, trade with level 3 projectiles, and has faster recovery than the generic fireball. Also unlike generic fireballs, this one travels fullscreen without fizzing out. Cell's Kantsu is also unique in that it's the only one that knocks down on hit. Also, because Cell is so tall, his Kantsu is incredibly hard to hop over, making it quite safe to throw out at a lot of ranges. Not a lot of projectiles can compete with this one.
Kamehameha - A - Cell throws a powerful energy blast diagonally up-forward. Generic anti-air projectile attack. Costs 10 health to perform. Does its job for the most part, too slow to use on reaction to hops but is still useful as a preemptive anti-air or on reaction to full jumps.
Chou-Kamehameha - A - KA! ME! HA! ME! HAAAAAAAAAAAAA! Standard chargeable projectile attack that most characters have in some form. Costs 10 health to perform. Hold down A while performing in order to charge it up to a maximum of 3 power values. No charge will quickly release a level 2 projectile. Medium charge will release a level 3 projectile. Maximum charge will release a highly damaging level 4 projectile. Cell's is unique in that the blast starts further away from his hands than other Kamehameha type attacks, making it better for zoning even though it whiffs at point blank range.
Desperation Attack: Bakuretsu Rush Y - Cell gets real mad and punches a lot. Second highest damage desperation in the game, and a good move to use on a stunned opponent midscreen, although in the corner you can get better damage.
Desperation Attack: Tri-Ground Eruption Y - Cell gets real mad and punches the ground, causing three geysers to fly up. Cell's other desperation attack. Not particularly useful, the slow start up makes it unusable in neutral and Bakuretsu Rush does more damage.