Dear OP, I spent 2 years researching below and I know what I'm talking about, people might have different opinions on an individual frame but these are MY opinions and MY experiences with each frame. It's a shame that I put in so much work to make this nice list and people are telling me my opinions are wrong, #gaming you're too funny. Ash is good for soloing missions like mobile defense or just spy, he's pretty tough to kill Atlas is the most aggressive UP IN YO FACE frame being primarily a melee frame (he's best though, huge shield) Banshee is pretty good in lower ranked missions, I wouldn't take her into anything above level 30 though. Chroma is about as average as they get in terms of damage / usefulness, MOSTLY useful in mobile defense missions Ember is also good in defense...and mobile defense...and survival....get ember. Equinox is an amazing warframe that can EASILY hold it's own (it's girl and boy) best in survival Excalibur is good. Nothing more to say, he's a beast with his energy sword skill that can kill anything from up to 20ft. Frost is obviously useful for one thing and one thing only....defense missions and he does a fine job at it Hydroid would be another good starting frame because he's fun to use but not useful for the team and definitely not tanky enough for his up close skills Ivara is also an average warframe that can do pretty good in mid-high range enemies (20-40) just don't use her in defense :/ Limbo is garbage. Worst frame in the game don't let ANYBODY tell you different. His skills are basically pulling you or enemies into a rift where you can't shoot them. It's seriously retarded when people play this guy. Don't be Limbo. Ever. Loki is a god. Be invisible the ENTIRE game and just wreck through and through. Best prime for any type of spy missions or hostage Mag is another garbage frame with no usefulness other than to pull items towards her for her team mates...yeah thanks. not. Mesa is another god but at Defense missions. Think of having a frame that is purely based off of getting 10x your regular damage and with headshots....at the speed of sound. Mirage is good for survival and defense missions with her 5x damage whenever she has her doppelgangers out, and her prism usually wipes out everything in the map in about 5 seconds. Nekros is sometimes required in survival on higher leveled enemies like on infested ships where he can just constantly spawn life support, health, and other items. Nezha I have no idea yet because I have not bothered to try her, but I know that she is another melee based frame and she has mixed reviews. Nova is yet another amazing frame where she can slow the enemies down to 25% their regular speed and making them walking bombs, you get a group of 20 enemies, prime them, shoot 1 in the head and they ALL blow up, she has very low defense though, good for any mission other than spy. Nyx is a mixed bag, she can control the AI but the AI is so retarded that it's really not worth it. Oberon is the final garbage frame that is not useful and does nothing to support his team, any trained warframe player can outdo an oberon player at any mission... Rhino is the tank frame, he has an ability where he just has a shell around him and he takes no damage, good for survival and very high leveled enemy areas Saryn is pretty average as well, she's not used in survival or defense missions...to be honest I don't see anyone ever being saryn, that must be a sign. Trinity is a MUST HAVE in high leveled survival / defense missions. To be able to heal your enemies at any given moment AND give them energy is awesome and essential. Valkyr is the berserker frame. You can get her from Alad V and I recommend you do this right away because she is one of the best frames in this game and is another melee frame, the more damage you do and take from enemy AI, the more resistance you get and soon enough you get high enough resistance you just stop taking damage from everyone. Valkyr is a must have frame Vaubon is extremely useful mixed with Nekros because he can throw a vortex that sucks all the enemies in and spins them around in 1 spot, it's like shooting fish in a barrel. Volt is a good solo frame being one of the fastest frames in the game (besides loki prime) with the highest amount of energy of any frame as well. Wukong is an EXTREMELY fun frame to play, if you ever watched naruto, he'll remind you of Money King: Enma with his large stick that get's bigger the more he hits people, not very useful for the team but fun none the less. Zephyr is weak, zephyr is though...like wukong, a fun class to play. Being the bird frame you can literally fly across the map in one huge jump and it's so fun, being able to spawn twisters too that shoot your enemy 30+ft in the sky is awesome. t;dr The best frame in my opinion is going to have to be Atlas. Because his punches knock down any enemy and make them vulnerable for a good 10 seconds while they try to get up only to be knocked down again. Plus when you punch a group, his punches make shock waves that hurt the other enemies. Mixed in with his HUGE shield and armor, he's definitely unstoppable. At least in my hands he is.

Rhino is straight beast. I love that frame. I just want the prime version.

The best frames are, in no particular order: Loki Nova Frost Rhino Trinity Valkyr Ash Nyx If you have at least 1 of these you might as well be considered a God if used right. even better if you have a prime version of them. That's not so say others aren't useful, in fact nearly every frame can be used to great effectiveness.

Personally my favorite for having fun and still doing well is my Loki Prime. Tons of energy to play around with and stealth is not as hard. Heck I've even learned how to make him worth something in defense missions. When I am going for the gold its probably either Nova Prime or Valkyr. Nova is a great frame for most situation as she can slow enemies and even her first skill can be a great way to jump into a fray and have them softened up. As for Valkyr.... Well she speaks for herself... Claw bound death machine that if built right can go full missions just clawing things apart.

Valkyr is my favorite. Perfect if you wanna inflict a shit ton of damage on large groups of enemies for long periods of time. Plus you can also buff teammates and debuff enemies. [spoiler]Plus she's got dat ass[/spoiler]

No clear "best"it really depends on your play style. But I think the clear standouts to me because I play solo a lot is frost and rhino. They are must haves. If you are going to buy one I suggest frost and just play through to the jackal boss you can farm him for rhino parts and get him PDQ for free.