One of the most famous objects in the sky is the dark nebula Barnard 33, more commonly known as the Horsehead Nebula. This is a tough object for visual observers due to the faintness of IC 434, however there have been reports of it being visible in a 4" telescope! One of the biggest problems it the bright glare from the bright star zeta orionis. (Alnitak)
Also visible in the above image are the NGC 2024 (the Flame Nebula, and just to the left of the Flame Nebula, is the reflection nebula IC 432. Between the Horsehead and the Flame, is the reflection nebula, NGC 2023.