There are three ideas for fan-games I have in mind that I've always wanted to see that, well, would be awesome. So I'll share it with you guys for the heck of it.
Dr. Mario Bros.
The name should tell you exactly what it is- a fusion of side-scrolling action and Dr. Mario. You could play as Dr. Mario OR Dr. Luigi (Click Here for my design on Dr. Luigi).
The Vitamin System
Vitamins would work similar to eggs in Yoshi's Island. You would find vitamin parts like you would find coins in either red, blue, or yellow (and green, purple, and orange as well) throughout levels. Your HUD would show you how many of each color vitamin part you have. Two certain easy-to-reach buttons would toggle through what combination of vitamins you would be shooting (for example, the A-key would toggle through the left color and the S-key would toggle through the right). Different vitamin combinations would have different effects on enemies or your environment. Also, some colors would be harder to find than others. Vitamins can be thrown like fireballs, but now (as explained above) have an ammunition system. Aiming would be similar to Contra or Metroid, but the mouse could be used alternatively.
Your enemies would now be a lot less like the common Goomba- now Viruses have taken over the scene. Viruses have two quality- size and color. Color determines what kind of vitamin effects them. For example, if there's a red Virus, it can only be killed if the vitamin thrown has red in it. Some Viruses might be two colors, so both colors of the vitamin come into play. Size determines how many vitamins it takes to defeat one Virus. The bigger they are, the harder they fall. An average Virus would take about three of its own color to destroy.
Health and Coins
Unlike an average Mario platformer, you have three to five HP. Stronger enemies do more damage. However, when coins are collected in levels, they can be spent on more HP in the overworld for a maximum of 15 HP.
Paper Mario Bros.
Sounds similar to Dr. Mario Bros, right? That doesn't mean it's different. This time, the classic elements of Paper Mario are combined with the original Super Mario Bros. It may sound similar to Super Paper Mario, but it's different alright.
Levels and Partners
The levels you play are not just the same levels from the original Super Mario Bros.- they are also the Lost Levels and Deluxe levels. However, every level will be extended somewhere within it by about 50%. This is to make more room for the use of partners.
Partners will play a very similar role to what they did in Paper Mario. They will be the original partners and will function in every same way, revealing secrets or helping Mario continue through tricky parts of a level.
Mario will bring back his spin, ground pound (including the spin pound), and hammer. These (like partners) will help Mario do things he could do before in the original adventures. For example, ground pounding can uncover Star Pieces (returning as a collectible) and break bricks. Using his hammer, he can stun enemies, hit switches, etc.
Mario will also be able to use Action Commands...
Mario's foes won't change from the original, but Paper Mario exclusive enemies like Cleft and Spinia will appear. This time, they will have HP. Mario now has use for the hammer (stunning enemies) and the Action Command , making for a much more interesting encounter with even Goombas. That's not all, enemies will follow and try to attack Mario when he comes near.
Badges and Items
These two elements will work the same as they did in Paper Mario, but will be adapted to work for a platformer.
Kirby's Epic Farm
A funny name, but a seriously awesome idea. Inspired by merging Pokemon and Kirby. I'll explain this quickly- it plays similar to Kirby's Adventure, but now, you can capture enemies upon inhaling them. Now, when you enter levels, you can take a party of captured enemies (like Sir Kibble, etc) to fight alongside you. As the game goes on, tons of enemies appear at once in each level, so copy abilities and your partners will come in handy.
Thoughts on these ideas?