(hex:7F) is a glitch item in Pokémon Red and Blue. It is an unterminated name glitch item, hence is applicable for Yami Shop glitch and other screen data related exploits.As it is an unterminated name glitch item, it has effects associated with those items, and can be used for screen data exploits like LOL glitch, Yami Shop glitch or will usually cause the TMTRAINER effect in battle.
When a 0x50 sub-tile is early enough on the screen and this glitch item is used outside of battle, the game may freeze.
Using this glitch item in battle typically results in the TMTRAINER effect due to the last 0x50 sub-tile being later in the screen data, but if this is forced to be earlier with the GameShark code 0150A0C3 (or theoretically OAM DMA hijacking), the game may also freeze.