I came up with this idea after rereading the comments on my other post, "If you could make up your own Mangekyou ability, what would it be?"
Mine would be タイムアイ (Time Eye). It would allow me to stop time for my opponent (kind of like genjutsu, but in actual reality) as I see fit, but can only be used at a maximum of 5 times a day, with a 5 minute time limit on each use. While time is frozen for my opponent, I can move around freely. This ability can be used on a maximum of 10 targets.
Basically, the same drawbacks as the Sharingan, which means eventual blindness, and after each use, my chakra levels are drained for however many minutes the dojutsu is used for, multiplied by 10. For example, if I were to use it for 1 minute, 10% of my chakra would be drained. If I were to use it for the full 5 minutes, 50% of my chakra would be drained.
My upgrade would be the 無限の時間の目 (Infinite Time Eye). Similar to the Eternal Mangkyou Sharingan, I would be able to use my abilities without the drawback of eventual blindness, but my use limit per day and time limit of use per day would be doubled. Also, the chakra cost of each use would be chopped in half. For example, if I were to use it for 1 minute, only 5% of my chakra would be consumed. If I were to use it for 5 minutes , only 25% of my chakra would be consumed. If I were to use it for 10 minutes, 50% of my chakra would be consumed. The Infinite Time Eye would be attained by killing someone close to you by using the ability.
My Dōjutsu would look like a regular eye, but the pupils would be white, with a ripple pattern of black circles inside of the pupil, almost like a Rinnegan. The Infinite Time Eye would have Yin-Yang symbols for pupils.
Well personally I don't really know if this would qualify as a dojutsu but if I had to create one it would be one that hybridizes the Sharingan, Byakugan, and Rinnegan. The eye itself would look identical to the sharingan (that is a red iris and one to three tomoe as ones use, skill, and chakra control develop) but with one key difference. Once had developed three tomoe each would act like a gate. Each gate would hold one of the Three Great Visual Jutsu. For example if the situation called for the sharingan one could activate the respective tomoe.
another potential candidate would be a dojutsu that allows one to use any of the seven chakra natures (fire, water, wind, lightning, earth, yin, and yang) in any combination that would be not result in contradictory results. We've all seen shinobi with Kekkei Genkai use two chakra natures at once (Haku, Roshi, and the former Mizukage to name but three examples) and two that can use three at once (Onoki and Mu both using Particles Style: wind, fire, and earth styles) called Kekkei Tōta. My idea is merely an extension of that but without needing an inherited Kekkei Genkai to do so. for various combinations of chakra natures consult the following (url: http://pre11.deviantart.net/6dbf/th/pre/i/2012/276/5/b/elemental_combinations_2_3_by_fg7dragon-d5gosiu.jpg)
When all ninja move in bullet time basically already, you don't think it's OP to have 1 minute of being able to do literally whatever you want to your opponent for only 10% of your chakra?
Yeah, that's why it would be a kekkei genkai, with an EXTREMELY hard unlocking process. I haven't figured it out yet though.
Edit: I would say you have to be a descendant of a clan, the Fukkatsu Clan, and you'd have to go through a process of sharing chakra with ten others, and the end result MIGHT (like a 2.5% chance) be with one ending up with the Time Eye. It would be as rare as the rinne-sharingan, with only two beings ever unlocking the dojutsu.