If the Gens32 Surreal is now the best SEGA Genesis, Mega-Drive (MD) emulator for Windows only, then Gens is the earliest and best one for Windows and Linux all the time. And it's a cross-platform, open-source Sega Genesis / Sega CD/ MD / Sega 32X emulator for DOS/Win32/UNIX.
Happy Chick Emulator (also called 小鸡模拟器) is a free versatile emulator APP from China I recently found. It makes playing video games on Android or iPhone never been easier. It not only has built in a variety of excellent emulators, we can also download any game ROM with one-click, all of which let us fondle admiringly.
TinyPiano.c is a simple yet satisfying piano emulator (turns your PC keyboard into an electronic piano), gives 15 tones max, with 120+ different sound effects, and sounds great. Besides, it is so tiny that even smaller than a blank word document.